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Therapeutic monoclonal antibodies (mAbs) are effective treatments for a range of cancers and other serious diseases, however mAb treatments cost on average ∼$100 000 per year per patient, limiting their use. Currently, industry favours Protein A affinity chromatography (PrAc) as the key step in downstream processing of mAbs. This step, although highly efficient, represents a significant mAb production cost. Fouling of the Protein A column and Protein A ligand leaching contribute to the cost of mAb production by shortening the life span of the resin. In this study, we assessed the performance of used PrAc resin recovered from the middle inlet, center and outlet as well as the side inlet of a pilot-scale industrial column. We used a combination of static binding capacity (SBC) analysis and Attenuated Total Reflection-Fourier Transform Infrared (ATR-FTIR) spectroscopy to explore the used resin samples. SBC analysis demonstrated that resin from the inlet of the column had lower binding capacity than resin from the column outlet. ATR-FTIR spectroscopy with PLS (partial least square) analysis confirmed the results obtained from SBC analysis. Importantly, in situ ATR-FTIR spectroscopy also allowed both measurement of the concentration and assessment of the conformational state of the bound Protein A. Our results reveal that PrAc resin degradation after use is dependent on column location and that neither Protein A ligand leaching nor denaturation are responsible for binding capacity loss., A combination of static binding capacity analysis and ATR-FTIR spectroscopy reveals that loss of binding capacity is not uniform through a used Protein A column and is not due to loss of Protein A ligand.

Advances in plasmonics have been fundamentally rooted in minimizing ohmic losses in metallic nanostructures. However, the losses at resonance can play a positive role; for instance, in optical heat...

Inter- and intramolecular interactions in multicomponent polymer systems influence their physical and chemical properties significantly and thus have implications on their synthesis and processing. In the present study, chemical images were obtained by plotting the peak position of a spectral band from the data sets generated using in situ attenuated total reflection Fourier transform infrared (ATR FT-IR) spectroscopic imaging. This approach was successfully used to visualize changes in intra- and intermolecular interactions in poly(3-hydroxybutyrate)/poly(L-lactic acid) (PHB/PLLA) blends during the isothermal melt crystallization. The peak position of ν(C＝O) band, which reflects the nature of the intermolecular interaction, shows that the intermolecular interactions between PHB and PLLA in the miscible state (1733 cm−1) changes to the inter- and intramolecular interaction (CH3⋯O=C, 1720 cm−1) within PHB crystal during the isothermal melt crystallization. Compared with spectroscopic images obtained by plotting the distribution of absorbance of spectral bands, which reveals the spatial distribution of blend components, the approach of plotting the peak position of a spectral band reflects the spatial distribution of different intra- and intermolecular interactions. With the process of isothermal melt-crystallization, the disappearance of the intermolecular interaction between PHB and PLLA and the appearance of the inter- and intramolecular interactions within the PHB crystal were both visualized through the images based on the observation of the band position. This work shows the potential of using in-situ ATR FT-IR spectroscopic imaging to visualize different types of inter- or intramolecular interactions between polymer molecules or between polymer and other additives in various types of multicomponent polymer systems., Graphical Abstract

Exposing polymers to high-pressure and supercritical CO2 is a useful approach in polymer processing. Consequently, the mechanisms of polymer–polymer interaction under such conditions are worthy of further investigation. Two-dimensional correlation analysis and two-dimensional disrelation mapping were applied to datasets of polycaprolactone –poly(lactic acid) blend with or without high-pressure CO2 obtained using in situ attenuated total reflection Fourier transform spectroscopic imaging. The relatively weak dipole–dipole intermolecular interactions between polymer molecules were visualized through the disrelation maps for the first time. Because of the specially designed polymer interface, the interactions between the same type of polymer molecules and different types of polymer molecules were differentiated. Under exposure to high-pressure CO2, all three types of interactions: interaction between polycaprolactone molecules and poly(lactic acid) molecules, interaction between polycaprolactone molecules and interaction between poly(lactic acid) molecules become weaker than those in the polymer interface without high-pressure CO2. The resulting increase in the Flory interaction parameter is the main cause of phase separation in the PCL–PLA blend under high-pressure CO2. The findings from this study will be of benefit for polymer processing with high-pressure and supercritical CO2.

This paper presents the results of study of titanium–magnesium catalysts often used in polymerization processes, by photoluminescence spectroscopy (PL) in combination with diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS). The interaction of dibutyl phthalate (DBP) with MgCl2was studied at DBPadded/Mg = 0–1 (mol/mol). The luminescence spectra with excitation at 278 nm and the excitation spectra for main emission bands were recorded. It was shown that DBP adsorbed on magnesium chloride, both in the form of donor–acceptor complexes (D+A–) and in the form of molecular complexes. At DBPadded/Mg +A–complexes occur predominantly; with an increase in DBPadded/Mg, the fraction of molecular complexes increases. Molecular complexes are destroyed during the treatment of the support by TiCl4. In this case, the structure of magnesium chloride is disordered and new coordination–unsaturated sites are formed. This work is a first attempt to apply PL spectroscopy in combination with DRIFTS spectroscopy to study titanium–magnesium Ziegler–Natta catalysts. The application of PL spectroscopy to such systems made it possible to detect interactions within and between donor molecules, which would be particularly challenging to achieve using other spectroscopic methods. Both spectroscopic methods provided crucial information about the existence of two types of complexes on the sample surface which is important for tuning the synthesis procedure of the titanium–magnesium catalysts for olefin polymerization.

The effects of hydration on the DNA conformation in the colon biopsy tissues at different disease stages, hyperplasia, dysplasia, and cancer, and their subsequent classifications were investigated in this study. FTIR spectroscopic imaging was used to study the tissues while controlling the humidity from 16% RH to 88% RH using saturated salt solutions. A nonuniform uptake of water into the tissue at its maximum hydrated state was observed in the chemical images showing the distribution of the absorbance of the νas OH spectral band. The regions of high absorbance of this band in the tissues overlap with the regions of high absorbance of predominantly the phosphate (1143-1100 cm-1) and lipid (2879-2844 cm-1) bands. Analysis of the second derivative spectra of the hydrated and dehydrated colon tissues further revealed significant peak shifts and changes in absorbance of the spectral bands that correspond to the vibrations of the phosphate group of DNA. These findings showed some disparities when compared to the effect of hydration on the infrared spectra of live cells and pure isolated DNA, possibly due to the presence of DNA mostly in its A-form in the formalin fixed tissues. Coupled with principal component analysis, the spectral biomarkers that differentiate the healthy colon tissues from the diseased tissues were identified to be in the phosphodiester spectral region (1300-1000 cm-1). This differentiation varied under different humidity conditions, with the highest sensitivity of ∼98% found at the dehydrated state of the tissues with random forest supervised classification.

Fourier transform infrared (FTIR) spectroscopic imaging of colon biopsy tissues in transmission combined with machine learning for the classification of different stages of colon malignancy was carried out in this study. Two different approaches, an optical and a computational one, were applied for the elimination of the scattering background during the measurements and compared with the results of the machine learning model without correction for the scattering. Several different data processing pathways were implemented in order to obtain a high accuracy of the prediction model. This study demonstrates, for the first time, that C–H stretching and amide I bands are of little to no significance in the classification of the colon malignancy, based on the Gini importance values by random forest (RF). The best prediction outcome is found when supervised RF classification was carried out in the fingerprint region of the spectral data between 1500 and 1000 cm−1 (excluding the contribution of amide I and II bands). An overall prediction accuracy higher than 90% is achieved through the RF. The results also show that dysplastic and hyperplastic tissues are well distinguished. This leads to the insight that the important differences between hyperplastic and dysplastic colon tissues lie within the fingerprint region of FTIR spectra. In this study, computational correction performed better than optical correction, but the findings show that the disease states of colon biopsies can be distinguished effectively without elimination of Mie scattering effect. Graphical abstract Electronic supplementary material The online version of this article (10.1007/s00216-019-02069-6) contains supplementary material, which is available to authorized users.

The depth of penetration and effective thickness in ATR-FTIR spectroscopic imaging are dependent on the wavelength and angle of incidence of the incoming light beam. We have demonstrated, for the first time, that variable angle micro ATR-FTIR, which is created via the insertion of circular apertures, is intrinsic at examining embedded components within a prostate tissue specimen. This is done by constructing a 3D model from the stacks of 2D chemical images obtained, each of which represents the spatial distribution of a chosen spectral band assigned to the component of interest at a different probing depth. ATR-FTIR imaging is also shown to have the ability to resolve subcellular components of cells such as organelles. For differentiation of diseased and non-diseased tissues, statistical tests are employed to analyse the spectral datasets obtained. When the second derivative of the spectral datasets was subjected to t-test analysis, the spectral differences between both samples in the fingerprint region are shown to be more significant at a shallow depth of penetration, with the greatest variance at the spectral band of 1235 cm-1 (vasPO2-), depicted by plotting the scores of PCA on its first two PCs. Overall, this paper demonstrates a non-destructive, label-free approach for examining heterogeneous biological samples in the z-direction to construct a 3D model using micro ATR-FTIR imaging, in a qualitative and semi-quantitative manner.

Superlensing plays a crucial role in near- and far-field optical imaging with sub-wavelength resolution. One of the ways to expand optical bandwidth is surface plasmon resonances in layered metal-dielectric nanostructures. These resonances are commonly excited at a tunable single frequency. In this study, we propose the concept of a multimode far-field superlens made of a titanium oxynitride (TiON) thin film, that is a disordered metal-dielectric refractory nano-composite. These films exhibit a double epsilon-near-zero (2-ENZ) behavior near the percolation threshold and, therefore, favor super-coupling the incident laser light to surface plasmon resonances, not using such couplers as a prism, a grating, etc. We experimentally observe stimulated Raman gain emission from nano-structured TiON thin films exposed to low-power continuous-wave laser light. It is shown that superresolution of

Biopharmaceuticals are used to treat a range of diseases from arthritis to cancer, however, since the advent of these highly specific, effective drugs, there have been challenges involved in their production. The most common biopharmaceuticals, monoclonal antibodies (mAbs), are vulnerable to aggregation and precipitation during processing. Freeze thaw cycles (FTCs), which can be required for storage and transportation, can lead to a substantial loss of product, and contributes to the high cost of antibody production. It is therefore necessary to monitor aggregation levels at susceptible points in the production pathway, such as during purification and transportation, thus contributing to a fuller understanding of mAb aggregation and providing a basis for rational optimisation of the production process. This paper uses attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy and spectroscopic imaging to investigate the effect of these potentially detrimental FTCs on protein secondary structure in both static wells and under flowing conditions, using lysozyme as a model protein. The results revealed that the amount of protein close to the surface of the ATR crystal, and hence level of aggregates, increased with increasing FTCs. This was observed both within wells and under flow conditions, using conventional ATR-FTIR spectroscopy and ATR-FTIR spectroscopic imaging. Interestingly, we also observed changes in the Amide I band shape indicating an increase in β-sheet contribution, and therefore an increase in aggregates, with increasing number of FTCs. These results show for the first time how ATR-FTIR spectroscopy can be successfully applied to study the effect of FTC cycles on protein samples. This could have numerous broader applications, such as in biopharmaceutical production and rapid diagnostic testing., ATR-FTIR spectroscopy and spectroscopic imaging was used in combination with PDMS flow cells, and effectively applied to monitor the effect of repeat freeze thaw cycles (FTCs) on protein secondary structure, revealing higher aggregate levels with increasing FTCs.

Molecular orientation of aromatic polyimides (PIs) and their precursor of poly(amic ester)s (PAE) in the biaxially oriented films were analyzed by polarized microscopic attenuated-total-reflection Fourier-transform infrared absorption spectroscopy (micro pATR-FTIR) imaging. The films were prepared by shearing a lyotropic liquid crystal (LC) solution of the PAE on a glass substrate and subsequent drying under a N2 flow, and the long axis of polymer chains were distributed around the shear direction. In the film, streak-shaped defects were observed along the shear direction with optical microscopy. Such structural heterogeneities on the micrometer (μm) scale are expected to be visualized in spatial distribution map of molecular orientation order acquired with micro pATR-FTIR imaging. In this study, uniaxial orientation order parameter, S, and a mean square cosine value, ⟨cos2ψ⟩, were used to quantify the degree of orientation of the PI main chain and that of aromatic imide plane, respectively. It was revealed that the films are apparently homogeneous in the spatial distribution map of the S, while the films exhibited obvious heterogeneity in that of ⟨cos2ψ⟩, in which “face-on” and “edge-on” orientation domains coexist. The results indicate that orientation direction of the rigid PI chains is fixed in the averaged orientation direction of the oriented PAE matrix during thermal imidization, while the aromatic imide ring can be rotated around the main chain. Furthermore, cracks in the PI film were successfully visualized by ATR-FTIR imaging, and the orientation distribution inside the cracks was investigated. Through this structural study, we validated the quantitative capability of the micro pATR-FTIR imaging method thorough the analyses of highly oriented PI films and demonstrated its ability to investigate μm-scale heterogeneity on the basis of molecular orientation analyses.

Modern bone tissue engineering is based on the use of implants in the form of biomaterials, which are used as scaffolds for osteoprogenitor or stem cells. The task of the scaffolds is to temporarily sustain the function, proliferation and differentiation of bone tissue to enable its regeneration. The aim of this work is to use the macro ATR-FTIR spectroscopic imaging for analysis of the ceramic-based biomaterial (chitosan/β-1,3-glucan/hydroxyapatite). Specifically, during long-term culture of mesenchymal cells derived from adipose tissue (ADSCs) and bone marrow (BMDSCs) on the surface of scaffold. Infrared spectroscopy allows the acquisition of information on both the organic and inorganic parts of the tested composite. This innovative spectroscopic approach proved to be very suitable for studying the formation of new bone tissue and ECM components, sample staining and demineralization are not required and consequently the approach is rapid and cost-effective. The novelty of this study focuses on the innovatory use of ATR-FTIR imaging to evaluate the molecular structure and maturity of collagen as well as mineral matrix formation and crystallization in the context of bone regenerative medicine. Our research has shown that the biomaterial investigated on this work facilitates the formation of valid bone ECM of the stem cells types studied, as a result of the synthesis of type I collagen and mineral content deposition. Nevertheless, ADSC cells have been proven to produce a greater amount of collagen with a lower content of helical secondary structures, at the same time showing a higher mineralization intensity compared to BMDSC cells. Considering the above results, it could be stated that the developed scaffold is a promising material for biomedical applications, including modification of bone implants to increase their biocompatibility.

Fourier transform infrared (FT-IR) spectroscopic imaging and microscopy of single living cells are established label-free technique for the study of cell biology. The constant driver to improve the spatial resolution of the technique is due to the diffraction limit given by infrared (IR) wavelength making subcellular study challenging. Recently, we have reported, with the use of a prototype zinc sulfide (ZnS) transmission cell made of two hemispheres, that the spatial resolution is improved by the factor of the refractive index of ZnS, achieving a λ/2.7 spatial resolution using the synchrotron–IR microscopy with a 36× objective with numerical aperture of 0.5. To refine and to demonstrate that the ZnS hemisphere transmission device can be translated to standard bench-top FT-IR imaging systems, we have, in this work, modified the device to achieve a more precise path length, which has improved the spectral quality of the living cells, and showed for the first time that the device can be applied to study live cells with three different bench-top FT-IR imaging systems. We applied focal plane array (FPA) imaging, linear array, and a synchrotron radiation single-point scanning method and demonstrated that in all cases, subcellular details of individual living cells can be obtained. Results have shown that imaging with the FPA detector can measure the largest area in a given time, while measurements from the scanning methods produced a smoother image. Synchrotron radiation single-point mapping produced the best quality image and has the flexibility to introduce over sampling to produce images of cells with great details, but it is time consuming in scanning mode. In summary, this work has demonstrated that the ZnS hemispheres can be applied in all three spectroscopic approaches to improve the spatial resolution without any modification to the existing microscopes.

Monoclonal antibodies (mAbs) have been used as therapeutics for the last few decades. It is necessary to investigate the stability of these mAbs under stress conditions and to elucidate aggregation mechanisms as a means of developing approaches which minimize the problem. Attenuated total reflection (ATR)-FTIR spectroscopic imaging allows probing of a sample at a depth of penetration of around 0.5-5 μm, which makes it suitable for the study of aggregated proteins when accumulated as a layer close to the surface of the ZnSe internal reflection element (IRE). Here, macro ATR-FTIR spectroscopic imaging, along with a variable angle of incidence accessory, have been used to differentiate between the secondary structure of proteins in bulk solution and those that have precipitated onto or near the ZnSe IRE surface. IgG spectra obtained from protein samples in individual wells have been averaged, extracted, and preprocessed, and the Amide I bands of the protein samples were compared and further analyzed to reveal protein distribution at the ZnSe IRE surface. These findings show depth profiling of IgG aggregates at the ZnSe IRE surface (0.5-5 μm) and do not follow a trend of decreasing protein presence with an increasing angle of incidence or increasing depth of penetration, suggesting an irregular distribution of aggregates in the z-direction.

Over the past decades, considerable progress has been made toward far-field optical imaging beyond the diffraction limit. However, most working proof-of-concepts are based on either time-consuming scanning of a subdiffraction focal spot over a sample or postrecovery treatment using a priori information on a sought image. To our knowledge, none of these can be regarded as being close to a perfect far-field superlensing system capable of real-time color imaging with subwavelength resolution. In this paper, we suggest a proof-of-concept for far-field nonlinear metalens that is made of a disordered metal–dielectric nanocomposite. Postoxidation of a refractory titanium nitride (TiN) thin film, used as a nonlinear plasmonic material, results in the formation of a titanium oxynitride (TiON) film comprising a mixture of multiple phases of TiOxNy. Due to a double epsilon-near-zero behavior near the percolation threshold, the TiON favors supercoupling of the incident light to surface plasmon resonance within the vi...

[Image: see text] The analytical study of historical collagen-based materials such as leather book covers is a complex task for conservation scientists. Historical leather presents a heterogeneous composition of both organic and inorganic materials that show an evident reactivity, particularly when exposed to specific environments. Its correct preservation in archival documents remains challenging as some aspects of its chemical composition, degradation, and effectiveness of conservation treatments are still not fully understood. Here, we describe a novel application of attenuated total reflection (ATR)–Fourier transform infrared spectroscopic imaging coupled with a macro ATR accessory to study historical leather book covers. This nondestructive and high spatial resolution approach has allowed the visualization of degradation phenomena affecting this fragile material, particularly the gelatinization of collagen and, for the first time, the detection of the formation of calcium stearate (metal carboxylates or soaps). In addition, the distribution of modified soybean oil used as a treatment to maintain properties such as elasticity and hydrophobicity of the leather was studied. The effect of anomalous dispersion on the strong IR bands obtained in the ATR mode and the resulting changes to the band positions are also discussed. This research addresses issues that are relevant to the conservation of archival materials of cultural heritage for future generations.

The triblock copolymer L121 [poly(ethylene glycol)5-block-poly(propylene glycol)68-block-poly(ethylene glycol)5], the room temperature ionic liquid BMIM BF4 (1-butyl-3-methylimidazolium tetrafluoroborate) and the polymer PEG-400 (polyethylene glycol-400) have been compared in their liquid state to test their sorption capability of CO2 by exposure to high-pressure gas for 3 h in a controlled system. The presence of the gas in the studied systems has been determined at atmospheric pressure in the temperature range 288.15–313.15 K by using near-infrared (NIR) spectroscopy. The CO2 sorption in BMIM BF4 and PEG-400 was very small and detectable up to 293.15 K, only L121 showed the CO2 typical bands in the NIR region of the spectra up to 313.15 K, thus a linear correlation can be obtained by plotting the CO2 absorbance of those bands as a function of temperature. The effect induced by temperature on the swelling degree of L121 copolymer has also been investigated.

High-pressure and supercritical CO2 (scCO2) have the potential to be employed as alternatives to organic solvents for processing polymeric materials. High-pressure and scCO2 offer advantages for polymer processing that include, inter alia, plasticisation, phase separation in blends, crystal modification, and swelling of polymers. These effects can be useful for selectively treating polymeric samples for a range of applications. This opinion paper will discuss the importance of Fourier transform infrared (FTIR) spectroscopy, in attenutated total reflection (ATR) mode, to aid the understanding of polymeric processing based on their unique molecular vibrations. This information is integral for developing more efficient processing pathways which will mean that the full potential of high-pressure and scCO2 processing can be realised. The current state-of-the-art will be reported that will include an overview of key recent advances utilising FTIR spectroscopy. Challenges and future areas of research will be outlined where new and exciting opportunities using this “green” processing technology will be predicted.

We report a new approach for infrared spectroscopic analysis of fiberglass materials using a mirror substrate, which allowed the specular reflection from the sample surface to be minimized and detect the light passing through the sample. The application of this technique for platinum-containing fiberglass catalysts made it possible for the first time to identify sulfate compounds formed in glass fibers during the oxidation reaction of sulfur dioxide. The developed technique can be applied for a number of research samples that are difficult to analyze by conventional IR spectroscopic methods.

In this work, the first use of a cellulose hydrogel film reconstituted from ionic liquid (IL) 1-butyl-3-methylimidazolium chloride for the fluorescent determination of a plant antimalarial endopero...

In situ characterisation of ionic liquids under a controlled environment has been performed in a high throughput manner using macro ATR-FTIR spectroscopic imaging. 14 different ionic liquids with cations 1-butyl-3-methylimidazolium ([C4mim]), 1-butyl-2,3-dimethylimidazolium ([C4mmim]) and 1-butyl-3-methylpyrrolidinium ([C4C1pyrr]) and anions hexafluorophosphate ([PF6]), tetrafluoroborate ([BF4]), bis(trifluoromethylsulfonyl)imide ([NTf2]), perchlorate ([ClO4]), trifluoromethanesulfonate ([CF3SO3]), nitrate ([NO3]), methanesulfonate ([CH3SO3]) and trifluoroacetate ([TA]) were studied. The ionic liquids were deposited onto the measuring surface of the ATR crystal in the corresponding accessory hosted in the FTIR imaging system. Then these samples were exposed to a controlled environment of toluene and water vapour and spectra acquired simultaneously. Changing the structure of the cation head group from [C4mim] to [C4mmim] or [C4C1pyrr] only had a small effect on the toluene absorption while increasing the length of the alkyl chain of the cation (e.g. [C10mim]) has shown a significant increase in toluene absorption. The ionic liquids with the anion [NTf2] were found to absorb the highest amount of toluene followed by [CF3SO3], then [PF6], [ClO4], [NO3] and [TA], and the lowest amount of toluene was absorbed in ionic liquids with [BF4] or [CH3SO3] anions. The amount of water absorbed increases in the order: [C4mim][CH3SO3] > [C4mim][TA] > [C4mim][NO3] > [C4mim][CF3SO3] > [C4mim][ClO4] ~ [C4mim][BF4] ~ [C4mmim][BF4] > [C10mim][BF4] > [C4mim][PF6] ~ [C4mmim][PF6] > [C4mim][NTf2] ~ [C4mmim][NTf2] ~ [C4C1pyrr][NTf2]. This work has demonstrated that spectroscopic imaging provides a platform for the simultaneous screening of multiple ionic liquids in situ, when under controlled environments.

Spectroscopic imaging of biomaterials and biological systems has received increased interest within the last decade because of its potential to aid in the detection of disease using biomaterials/biopsy samples and to probe the states of live cells in a label-free manner. The factors behind this increased attention include the availability of improved infrared microscopes and systems that do not require the use of a synchrotron as a light source, as well as the decreasing costs of these systems. This article highlights the current technical challenges and future directions of mid-infrared spectroscopic imaging within this field. Specifically, these are improvements in spatial resolution and spectral quality through the use of novel added lenses and computational algorithms, as well as quantum cascade laser imaging systems, which offer advantages over traditional Fourier transform infrared systems with respect to the speed of acquisition and field of view. Overcoming these challenges will push forward spectroscopic imaging as a viable tool for disease diagnostics and medical research. Graphical abstract Absorbance images of a biopsy obtained using an FTIR imaging microscope with and without an added lens, and also using a QCL microscope with high-NA objective.

An application of disrelation mapping to Fourier transform infrared (FT-IR) spectroscopic imaging datasets is provided to reveal different H-bonded water species within a mammalian cell. 2D correlation analysis revealed a disrelation peak at (3420 cm-1, 3220 cm-1), showing the existence of a specific water band at around 3220 cm-1 whose variation of absorbance did not follow the trend of water molecules with a well-coordinated H-bonding network. Disrelation maps constructed with disrelation intensities between (3420 cm-1, 3220 cm-1) and (3420 cm-1, 1540 cm-1) reveal that the disruption of the water network occurs around the interfacial regions between the cell and media, indicating the disintegration of the H-bonding network of bulk water due to the entrapment of water by the protein inside the cell. This hydration effect also becomes apparent around the area adjacent to the cellular nucleus, reflecting the fact that protein synthesis mainly occurs in this region. These results clearly show the presence of different molecular states of water inside living cells, which are not readily identified by conventional analysis methods.

Non-equilibrium behavior of liquid mixture of polyethylene glycol (PEG) and polypropylene glycol (PPG) is studied. During the phase variation of PEG/PPG mixture, time-resolved Fourier transform infrared (FTIR) spectra were collected by attenuated total reflection (ATR) technique to selectively capture the development and subsequent variation of PEG-rich phase, appearing within a layer of the sample adjacent to the measuring surface of the ATR diamond prism. The FTIR spectra were then subjected to a two-dimensional (2D) correlation method to elucidate subtle but important changes in the absorbance of spectral bands. 2D correlation spectra revealed fine details of the non-equilibrium system. During the phase variation, dissociation between PEG and PPG generates free PEG molecules first. The emergence of the free PEG molecules triggers the subsequent self-assembly via the development of intermolecular H-bonding between PEG molecules, which eventually generates bigger PEG aggregates.

The approach for quantitative estimation of asphaltene sizes in crude oils in situ via precise simulation of electron spin resonance (ESR) spectra of the slowly rotating VO2+-containing fragments was developed. The method is based on the correlation between the size of the paramagnetic particles and their characteristic rotational time that can be determined by ESR in situ while incomplete averaging of anisotropic hyperfine interactions is observed. The precise simulation of the ESR spectra of heavy molecules, labeled naturally with vanadyl ions, allows one to find their size distribution in crude oils. In particular, the method is demonstrated to be an effective tool for the quantitative determination of the asphaltene sizes in different oil fractions in situ.

A new large-area germanium ATR crystal is utilised with an FTIR microscope to improve the acquired images of de-paraffinized colon biopsy sections, without recourse to a synchrotron source. The large crystal (⌀ = 28 mm) offers significant improvements compared to slide-on small germanium crystal (⌀ = 3.5 mm); for example, it facilitates more uniform distribution of higher signal intensity within the field of view and more rapid acquisition time. Mapping of a larger sample area up to ca. 350 × 350 μm2 with this new set-up, coupled with imaging using an FPA detector, is demonstrated for the first time on biological specimens. The performance of k-means clustering algorithm applied to classify the different anatomical structures of the colon biopsies is greatly improved with mapping. Comparison of H&E stained adjacent tissue sections with false-colour k-means images strongly support differentiation of five distinct regions within tissues. The efficiency of the methodology to categorise colon tissues at various stages of malignancy is analysed via multivariate chemometrics. The second derivative spectra extracted from the crypt region of the colon were subjected to Partial Least Squares classification. Good separation between data in clusters occurs when projecting spectra on a PLS score plot on a plane made by the first 3 principal components. Important spectral biomarkers for colon malignancy classification were identified to exist mostly in the fingerprint region of the FTIR spectrum based on the chemometrics analysis.

Activated carbons (ACs) show great potential for selective adsorption removal of sulfur (SARS) from hydrocarbon fuels but require improvements in uptake and selectivity. Moreover, systematic equilibria and kinetic analyses of ACs for desulfurization are still lacking. This work examines the influence of modifying a commercial-grade activated carbon (AC) by CO2 and steam treatment for the selective adsorption removal of dibenzothiophene (DBT) and 4,6-dimethyldibenzothiophene (4,6-DMDBT) at 323 K. An untreated AC and a charcoal Norit carbon (CN) were used for comparative purposes. Physicochemical characterization of the samples was carried out by combining N2-physisorption, X-ray diffractometry, microscopy, thermogravimetric and infrared analyses. The steam and CO2 treated ACs exhibited higher sulfur uptakes than the untreated AC and CN samples. The steam treated AC appears to be especially effective to remove sulfur, showing a remarkable sulfur uptake (~24 mgS·gads−1 from a mixture of 1500 ppmw of DBT and 1500 ppm 4,6-DMDBT) due to an increased surface area and microporosity. The modified ACs showed similar capacities for both DBT and the sterically hindered 4,6-DMDBT molecules. In addition, they were found to be selective in the presence of sulfur-free aromatics and showed good multicycle stability. Compared to other adsorbents, the modified ACs exhibited relatively high adsorption capacities. The combination of batch and fixed bed measurements revealed that the adsorption sites of the samples are characterized as heterogeneous due to the better fit to the Freundlich isotherm. The kinetic breakthrough profiles were described by the linear driving force (LDF) model.

This perspective paper discusses the recent and potential developments in the application of infrared spectroscopic imaging, with a focus on Fourier transform infrared (FTIR) spectroscopic imaging. The current state-of-the-art has been briefly reported, that includes recent trends and advances in applications of FTIR spectroscopic imaging to biomedical systems. Here, some new opportunities for research in the biomedical field, particularly for cancer diagnostics, and also in the engineering field of process analysis; as well as challenges in FTIR spectroscopic imaging are discussed. Current and future prospects that will bring spectroscopic imaging technologies to the frontier of advanced medical diagnostics and to process analytics in engineering applications will be outlined in this opinion paper.

Concentration profiles of water, polymer and plasticizer in the vicinity of the membrane/water interface were studied by in situ ATR-FTIR spectroscopic imaging with Cd2+-selective membranes as a model system. Two membrane compositions have been studied, both contained polyvinylchloride (PVC) as matrix, 2-nitrophenyl octyl ether (oNPOE) as plasticizer, Cd2+-selective neutral ionophore ETH 1062, and cadmium tetrakis (p-Cl-phenyl)borate as ion-exchanger. One of the membranes contained also a lipophilic electrolyte ETH 500. Prior to measurements, the membranes with overall thickness of 700 μm were equilibrated with water for 1 week. It is shown that in the membranes the surface layers with a thickness of 150 μm are enriched with water, whereas in the bulk of the membranes practically no water was detected. Overall water uptake and also kinetics of evaporation of absorbed water have been studied gravimetrically. Much slower process of leak of the membrane components to water was studied by UV–Vis absorption spectroscopy and gravimetrically, and ion-exchanger and plasticizer are identified as leaking components.

Studies of phase separation in lower critical solution temperature (LCST) polymer blends exposed to high-pressure CO2 provide an insight to their physical properties. Through using in situ high-pressure ATR-FTIR spectroscopic imaging, this work visualized the dynamic process of phase separation in Polycaprolactone (PCL)/Poly (lactic acid) (PLA) blend under high-pressure CO2 for the first time. ATR-FTIR spectroscopic images revealed that phase separation in PCL/PLA blends occurs with increasing temperature or upon exposure to high-pressure CO2. The change in the morphology of PCL-rich and PLA-rich domains in the ATR-FTIR spectroscopic images can be used to compare the extent of phase separation under different conditions. It is found that the extent of phase separation in PCL/PLA blends under high-pressure CO2 is enhanced with increasing temperature, CO2 pressure and exposure time. The effect of different molecular weights of one blend component, PCL, on the phase separation in PCL/PLA blends was also studied. This pioneering methodology opens possibilities to visualize the process of phase separation in LCST polymer blend systems and it can also be applied to study the process of interdiffusion in upper critical solution temperature (UCST) polymer blends.

Attenuated Total Reflection Fourier Transform Infrared (ATR-FTIR) spectroscopy is a label-free, non-destructive technique that can be applied to a vast range of biological applications, from imaging cancer tissues and live cells, to determining protein content and protein secondary structure composition. This review summarises the recent advances in applications of ATR-FTIR spectroscopy to biopharmaceuticals, the application of this technique to biosimilars, and the current uses of FTIR spectroscopy in biopharmaceutical production. We discuss the use of ATR-FTIR spectroscopic imaging to investigate biopharmaceuticals, and finally, give an outlook on the possible future developments and applications of ATR-FTIR spectroscopy and spectroscopic imaging to this field. Throughout the review comparisons will be made between FTIR spectroscopy and alternative analytical techniques, and areas will be identified where FTIR spectroscopy could perhaps offer a better alternative in future studies. This review focuses on the most recent advances in the field of using ATR-FTIR spectroscopy and spectroscopic imaging to characterise and evaluate biopharmaceuticals, both in industrial and academic research based environments., Graphical abstract Unlabelled Image, Highlights • This review article summarises the recent advances in applications of ATR-FTIR spectroscopy to biopharmaceuticals, the application of this technique to biosimilars, and the current uses of FTIR spectroscopy in biopharmaceutical production.

To evaluate new applications of cellulose hydrogel films prepared via the dissolution-regeneration of microcrystalline cellulose in two hydrophilic ionic liquids – 1-butyl-3-methylimidazolium acetate (BmimAc) and chloride (BmimCl), their optical, mechanical, and adsorption properties were concurrently studied and compared for the first time. The mild conditions under which both films were optically transparent and easy to handle were found. The BmimAc-reconstituted films exhibited an increased tensile strength and elongation at break of 9.5 and 2.5 times, respectively, than the BmimCl-reconstituted films. Due to the sponge-like morphology of the surface, BmimAc-reconstituted films demonstrate enhanced adsorption ability with respect to indigo carmine that is widely applied for industrial needs. This finding opens up opportunities for their use as an adsorbent for dyes. BmimCl-reconstituted films appeared to be a more promising material for the noncovalent immobilization of pyronin B, which is a component of the optical indicator systems for detecting different biologically active compounds.

This work reports new physical insights of the thermodynamic parameters and mechanisms of possible interactions occurring in polymers subjected to high-pressure CO2. ATR-FTIR spectroscopy has been used in situ to determine the thermodynamic parameters of the intermolecular interactions between CO2 and different functional groups of the polymers capable of specific interactions with sorbed CO2 molecules. Based on the measured ATR-FTIR spectra of the polymer samples subjected to high-pressure CO2 (30 bar) at different temperatures (300-340 K), it was possible to characterize polymer-polymer and CO2-polymer interactions. Particularly, the enthalpy and entropy of the formation of the specific non-covalent complexes between CO2 and the hydroxy (-OH), carbonyl (C[double bond, length as m-dash]O) and hydroxyimino ([double bond, length as m-dash]N-OH) functional groups of the polymer samples have been measured. Furthermore, the obtained spectroscopic results have provided an opportunity for the structure of these complexes to be proposed. An interesting phenomenon regarding the behavior of CO2/polymer systems has also been observed. It has been found that only for the polyketone, the value of enthalpy was negative indicating an exothermic process during the formation of the CO2-polymer non-covalent complexes. Conversely, for the polyoxime and polyalcohol samples there is a positive enthalpy determined. This is a result of the initial polymer-polymer interactions requiring more energy to break than is released during the formation of the CO2-polymer complex. The effect of increasing temperature to facilitate the breaking of the polymer-polymer interactions has also been observed. Hence, a mechanism for the formation of CO2-polymer complexes was suggested based on these results, which occurs via a two-step process: (1) the breaking of the existing polymer-polymer interactions followed by (2) the formation of new CO2-polymer non-covalent interactions.

Parvez Haris opened the discussion of the introductory lecture by Max Diem: Varying degrees of accuracy have been obtained for discrimination between cancerous and non-cancerous tissues using vibrational spectroscopic methods. What are the explanations for these variation in accuracy between cancerous and non-cancerous tissues and how do they correlate with accuracy from other techniques including histopathology?

Histopathology of tissue samples is used to determine the progression of cancer usually by staining and visual analysis. It is recognised that disease progression from healthy tissue to cancerous is accompanied by spectral signature changes in the mid-infrared range. In this work, FTIR spectroscopic imaging in transmission mode using a focal plane array (96 × 96 pixels) has been applied to the characterisation of Barrett's oesophageal adenocarcinoma. To correct optical aberrations, infrared transparent lenses were used of the same material (CaF2) as the slide on which biopsies were fixed. The lenses acted as an immersion objective, reducing scattering and improving spatial resolution. A novel mapping approach using a sliding lens is presented where spectral images obtained with added lenses are stitched together such that the dataset contained a representative section of the oesophageal tissue. Images were also acquired in transmission mode using high-magnification optics for enhanced spatial resolution, as well as with a germanium micro-ATR objective. The reduction of scattering was assessed using k-means clustering. The same tissue section map, which contained a region of high grade dysplasia, was analysed using hierarchical clustering analysis. A reduction of the trough at 1077 cm−1 in the second derivative spectra was identified as an indicator of high grade dysplasia. In addition, the spatial resolution obtained with the lens using high-magnification optics was assessed by measurements of a sharp interface of polymer laminate, which was also compared with that achieved with micro ATR-FTIR imaging. In transmission mode using the lens, it was determined to be 8.5 μm and using micro-ATR imaging, the resolution was 3 μm for the band at a wavelength of ca. 3 μm. The spatial resolution was also assessed with and without the added lens, in normal and high-magnification modes using a USAF target. Spectroscopic images of cells in transmission mode using two lenses are also presented, which are necessary for correcting chromatic aberration and refraction in both the condenser and objective. The use of lenses is shown to be necessary for obtaining high-quality spectroscopic images of cells in transmission mode and proves the applicability of the pseudo hemisphere approach for this and other microfluidic systems.

The intrinsic symmetry and orientation of single molecules play a crucial role in enhanced optical spectroscopy and nanoscopic imaging. Unlike bulk materials, in which all molecular orientations are unavoidably averaged in the far-field, intensities of vibrational modes in tip-enhanced Raman scattering (TERS) depend greatly on the polarization direction of near-field light. It means that a near-field Raman “dichroism” becomes possible for anisotropic single molecules. Quantitative evaluation of the molecular orientation gets complicated by the depolarization of TERS intensities. Clearly, the depolarization effect is enhanced with an optical antenna and/or a substrate due to their anisotropic origin. In this study, we provide theoretical and experimental insights into Raman tensors of a single azobenzene chromophore, a Disperse Orange 3 (DO3) molecule, supported with a glass base. It is shown that the Raman intensities of the spectral bands corresponding to symmetric and antisymmetric vibrations of the DO3 molecule, for example, –NO2 and –NH2 moieties, behave differently on the nanoscale. In particular, three-dimensional far- and near-field Raman diagrams indicate that antisymmetric vibrations become highly depolarized, whereas symmetric vibrations remain unchangeable but intensities of their spectral bands are enhanced. Here, we introduce a near-field depolarization factor defined as a normalized discrepancy of longitudinal and transverse TERS signals. We believe that our first steps will ultimately lead to advanced facilities of TERS spectroscopy and nanoscopy, related to the orientation of anisotropic single molecules and their symmetries.

Vibrational spectroscopies, based on Infrared absorption and/or Raman scattering provide a detailed fingerprint of a material, based on the chemical content. Diagnostic and prognostic tools based on these technologies have the potential to revolutionise our clinical systems leading to improved patient outcome, more efficient public services and significant economic savings. However, despite these strong drivers, there are many fundamental scientific and technological challenges which have limited the implementation of this technology in the clinical arena, although recent years have seen significant progress in addressing these challenges. This review examines (i) the state of the art of clinical applications of infrared absorption and Raman spectroscopy, and (ii) the outstanding challenges, and progress towards translation, highlighting specific examples in the areas of in vivo, ex vivo and in vitro applications. In addition, the requirements of instrumentation suitable for use in the clinic, strategies for pre-processing and statistical analysis in clinical spectroscopy and data sharing protocols, will be discussed.Emerging consensus recommendations are presented, and the future perspectives of the field are assessed, particularly in the context of national and international collaborative research initiatives, such as the UK EPSRC Clinical Infrared and Raman Spectroscopy Network, the EU COST Action Raman4Clinics, and the International Society for Clinical Spectroscopy.

We investigate the environmental stability of fullerene solutions by static and dynamic light scattering, FTIR, NMR and mass spectroscopies, and quantum chemical calculations. We find that visible light exposure of fullerene solutions in toluene, a good solvent, under ambient laboratory conditions results in C 60 oxidation to form fullerene epoxides, and subsequently causes fullerene clustering in solution. The clusters grow with time, even in absence of further illumination, and can reach dimensions from ≈ 100 nm to the μ m scale over ≈ 1 day. Static light scattering suggests that resulting aggregates are fractal, with a characteristic power law ( d f ) that increases from approximately 1.3 to 2.0 during light exposure. The clusters are bound by weak Coulombic interactions and are found to be reversible, disintegrating by mechanical agitation and thermal stress, and reforming over time. Our findings are relevant to the solution processing of composites and organic photovoltaics, whose reproducibility and performance requires control of fullerene solution stability under storage conditions.

Vibrational spectroscopic imaging and mapping approaches have continued in their development and applications for the analysis of pharmaceutical formulations. Obtaining spatially resolved chemical information about the distribution of different components within pharmaceutical formulations is integral for improving the understanding and quality of final drug products. This review aims to summarise some key advances of these technologies over recent years, primarily since 2010. An overview of FTIR, NIR, terahertz spectroscopic imaging and Raman mapping will be presented to give a perspective of the current state-of-the-art of these techniques for studying pharmaceutical samples. This will include their application to reveal spatial information of components that reveals molecular insight of polymorphic or structural changes, behaviour of formulations during dissolution experiments, uniformity of materials and detection of counterfeit products. Furthermore, new advancements will be presented that demonstrate the continuing novel applications of spectroscopic imaging and mapping, namely in FTIR spectroscopy, for studies of microfluidic devices. Whilst much of the recently developed work has been reported by academic groups, examples of the potential impacts of utilising these imaging and mapping technologies to support industrial applications have also been reviewed.

A novel infrared (IR) thermo-spectroscopic imaging technique is applied to the simultaneous measurements of IR transmittance spectroscopic images and thermal emission images of heat and mass transfers of styrene monomer polymerization in microfluidics. The heat released is observed in the mixing layer between two laminar flows of styrene monomer and toluene containing an initiator for polymerization. The concentration of chemical species and the independently measured temperature distribution within the mixing layer are determined at the microscale. This is the first report, of such a non-invasive method, to determine both the chemical composition and temperature distribution in microfluidic chemical reactions.

We consider a nonlinear mechanism of localized light inelastic scattering within nanopatterned plasmonic and Raman-active titanium nitride (TiN) thin films exposed to continuous-wave (cw) modest-power laser light. Owing to the strong third-order nonlinear interaction between optically excited broadband surface plasmons and localized Stokes and anti-Stokes waves, both stimulated and inverse Raman effects can be observed. We provide experimental evidence for coherent amplification of the localized Raman signals using a planar square-shaped refractory antenna.

This paper reviews the primary literature reporting the use of ionic liquids (ILs) in optical sensing technologies. The optical chemical sensors that have been developed with the assistance of ILs are classified according to the type of resultant material. Key aspects of applying ILs in such sensors are revealed and discussed. They include using ILs as solvents for the synthesis of sensor matrix materials; additives in polymer matrices; matrix materials; modifiers of the surfaces; and multifunctional sensor components. The operational principles, design, texture, and analytical characteristics of the offered sensors for determining CO2, O2, metal ions, CN-, and various organic compounds are critically discussed. The key advantages and disadvantages of using ILs in optical sensing technologies are defined. Finally, the applicability of the described materials for chemical analysis is evaluated, and possibilities for their further modernization are outlined.

This work highlights a mechanism for inducing axial anisotropy in side-chain nitroazobenzene (NAB) polymer thin films based on the combined effect of both local dc electrical poling and the longitudinal optical near-field. We show that highly anisotropic NAB chromophores are effectively oriented in the glassy environment under optical pumping with 632.8 nm excitation wavelength, which is out of the absorption band of chromophores. Axial anisotropy across the polymer thin film and its non-centrosymmetric behavior beyond the diffraction limit are experimentally rendered with tip-enhanced Raman scattering microscopy and scanning Kelvin probe microscopy.

The purpose of this review article is to outline the recent progress in near-infrared (NIR) imaging technology with particular emphasis on new instrumentation. Superior features of NIR imaging such as suitability for nondestructive and in-situ analysis, transmission ability, availability of optical fibers, high-speed monitoring and stability are very attractive not only for laboratory-based studies but also for diverse practical applications. In this review, introduction to chemical imaging is described, and then, a comparison among NIR, infrared (IR) and Raman imaging are made. Furthermore, the features of new NIR imaging instruments developed by our research group in collaboration with Yokogawa Electric Corporation and Sumitomo Electric Industries, Ltd. are discussed. Finally, some examples of applications of NIR imaging are introduced. Particularly, the performance and usefulness of the newly-developed imaging devices are demonstrated through their applications to pharmaceutical tablets and polymers.

Infrared spectroscopy and spectroscopic imaging, are robust, label free and inherently non-destructive methods with a high chemical specificity and sensitivity that are frequently employed in forensic science research and practices. This review aims to discuss the applications and recent developments of these methodologies in this field. Furthermore, the use of recently emerged Fourier transform infrared (FT-IR) spectroscopic imaging in transmission, external reflection and Attenuated Total Reflection (ATR) modes are summarised with relevance and potential for forensic science applications. This spectroscopic imaging approach provides the opportunity to obtain the chemical composition of fingermarks and information about possible contaminants deposited at a crime scene. Research that demonstrates the great potential of these techniques for analysis of fingerprint residues, explosive materials and counterfeit drugs will be reviewed. The implications of this research for the examination of different materials are considered, along with an outlook of possible future research avenues for the application of vibrational spectroscopic methods to the analysis of forensic samples.

Azobenzene-functionalized polymer films are functional materials, where the (planar vs. homeotropic) orientation of azo-dyes can be used for storing data. In order to characterize the nanoscale 3D orientation of the pigments in sub-10 nm thick polymer films we use two complementary techniques: polarization-controlled tip-enhanced Raman scattering (TERS) microscopy and contact scanning capacity microscopy. We demonstrate that the homeotropic and planar orientations of the azo-dyes are produced by applying a local dc electrical field and a resonant longitudinal optical near-field, respectively. For a non-destructive probe of the azo-dye orientation we apply a non-resonant optical near-field and compare the intensities of the Raman-active vibrational modes. We show that near-field Raman dichroism, a characteristic similar to the absorption dichroism used in far-field optics, can be a quantitative indicator of the 3D molecular orientation of the azo-dye at the nanoscale. This study directly benefits the further development of photochromic near-field optical memory that can lead to ultrahigh density information storage.

We demonstrate, for the first time, the application of FTIR spectroscopic imaging approach in situ to monitor the precipitation process of oil asphaltenes, induced by n-heptane under flow using microfluidic devices. The aggregation of asphaltenes induced by n-heptane flow with subsequent precipitation and formation of the deposits was studied for solution containing 5 wt % of asphaltenes in benzene. The FTIR spectroscopic approach with an array detector allowed us to assess the spatial distribution of the chemical components and their amounts in the system and display the process of aggregates formation with a spatial resolution of few micrometres. This chemical imaging technique shows that the flow of heptane results in non-equilibrium condition when the local content of the flocculants reaches the threshold amount needed for the asphaltenes aggregation. The relatively slow process of heptane diffusion into the benzene induces the asphaltenes aggregation followed by their precipitation and compaction. Fast asphaltene aggregation process under heptane flow leads to the formation of the deposit firmly fixed to the surface, while the precipitates formed during the diffusion process of heptane into the benzene can be easily taken from the channel. The FTIR spectroscopic imaging of the deposits formed revealed the spatial inhomogeneity of the precipitated asphaltenes in the direction of the heptane flow in microfluidic channel which is reflected in their different chemical composition and the presence of different functional groups (CH2–CH3, C O, S O). In particular, it was found that asphaltenes of different types and different CH2/CH3 ratios gradually start to precipitate in the direction of n-heptane flow. The data obtained demonstrate the importance of local concentration of flocculants as well as local characteristics of the system for asphaltenes aggregation, and overall precipitation process in flow regime.

A novel technique called disrelation spectroscopic imaging describes the process of identifying an area where a coordinated or out-of-phase change in pattern of spectral absorbance occurs. Disrelation mapping can be viewed as a spatial filter based on the well-established two-dimensional (2D) correlation function to highlight specific areas where disrelated variation occurs between ν1 and ν2. Disrelation intensity develops only if the spectral absorbance measured at ν1 and ν2 vary out of phase with each other within a specific spatial area. The disrelation mapping locates regions where absorbance varies in a dissimilar manner because of the contribution from species of different physical or chemical origins. Consequently, it becomes possible to probe onset of molecular interactions or presence of intermediate forms between components, which is not fully detected by the conventional visualizations based on a single wavenumber. Data analysis using disrelation mapping applied to Fourier transform infrared (FT-IR) spectroscopic images is presented in this study. Data sets of FT-IR spectroscopic images of blends of poly(methyl methacrylate) (PMMA) and polyethylene glycol (PEG) were subjected to the disrelation mapping. It was found that the disrelation intensity between 1730 and 1714 cm–1 becomes especially acute around the spatial boundary between PMMA and PEG domains within the studied blend sample. Thus the band at 1730 cm–1 most likely represents the C=O stretching mode of the C=O···H–O species due to the intermolecular hydrogen bonding between PMMA and PEG. The appearance of such disrelation is more noticeable in the PEG-rich region, for the PEG with low molecular weight. Consequently, it suggests that the blends of PMMA and PEG are partially miscible at the molecular level and these intermolecular interactions are affected by the quantity of the terminal –OH groups of the PEG.