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Spent coffee grounds (SCGs) are waste residues arising from the process of coffee brewing and are usually sent to landfills, causing environmental concerns. SCGs contain a considerable amount of fatty acids and is therefore a promising green alternative bio-based phase change material (PCMs) compared to conventional organic and inorganic PCMs. In this study, the extraction of coffee oil from SCGs was conducted using three different organic solvents-ethanol, acetone, and hexane. The chemical composition, chemical, and thermophysical properties of these coffee oil extracts were studied to evaluate their feasibility as a bio-based PCM. Gas chromatography-mass spectroscopy (GC-MS) analysis indicated that coffee oil contains about 60-80 % of fatty acids while the phase transition temperature of the coffee oil extracts is approximately 4.5 ± 0.72 °C, with latent heat values of 51.15 ± 1.46 J/g as determined by differential scanning calorimetry (DSC). Fourier Transform Infrared Spectroscopy (FTIR) and DSC results of coffee oil extracts after thermal cycling revealed good thermal and chemical stability. An application study to evaluate coffee oil extract as a potential cold therapy modality showed that it can maintain temperatures below normal body temperature for up to 46 min. In conclusion, this work exemplifies the potential of SCGs as a promising green and sustainable resource for bio-based PCMs for low-temperature thermal energy storage applications such as cold-chain transportation and cold therapy.

Propagation of ultrasonic wave in Carbon Fiber Reinforced Polymer (CFRP) is greatly influenced by the material’s matrix, resins and fiber volume ratio. Laser ultrasonic broadband spectral technique has been demonstrated for porosity and fiber volume ratio extraction on unidirection aligned CFRP laminates. Porosity in the matrix materials can be calculated by longitudinal wave attenuation and accurate fiber volume ratio can be derived by combined velocity through the high strength carbon fiber and the matrix material with further consideration of porosity effects. The results have been benchmarked by pulse-echo ultrasonic tests, gas pycnometer and thermal gravimetric analysis (TGA). The potentials and advantages of the laser ultrasonic technique as a non-destructive evaluation method for CFRP carbon fiber volume fraction evaluation were demonstrated.

To curb the spread of the COVID‐19 virus, the use of face masks such as disposable surgical masks and N95 respirators is being encouraged and even enforced in some countries. The widespread use of masks has resulted in global shortages and individuals are reusing them. This calls for proper disinfection of the masks while retaining their protective capability. In this study, the killing efficiency of ultraviolet‐C (UV‐C) irradiation, dry heat, and steam sterilization against bacteria (Staphylococcus aureus), fungi (Candida albicans), and nonpathogenic virus (Salmonella virus P22) is investigated. UV‐C irradiation for 10 min in a commercial UV sterilizer effectively disinfects surgical masks. N95 respirators require dry heat at 100 °C for hours while steam treatment works within 5 min. To address the question on safe reuse of the disinfected masks, their bacteria filtration efficiency, particle filtration efficiency, breathability, and fluid resistance are assessed. These performance factors are unaffected after 5 cycles of steam (10 min per cycle) and 10 cycles of dry heat at 100 °C (40 min per cycle) for N95 respirators, and 10 cycles of UV‐C irradiation for surgical masks (10 min per side per cycle). These findings provide insights into formulating the standard procedures for reusing masks without compromising their protective ability., The ongoing coronavirus pandemic has resulted in global shortages of disposable face masks, prompting them to be reused. To ensure safe reuse, masks undergo various disinfection methods including ultraviolet‐C irradiation, dry heat, and steam sterilization. Particularly, five cycles of steam treatment (10 min per cycle) do not impair the filtration capabilities, breathability, and fluid resistance property of N95 respirators.

Phosphide-based thermoelectrics are a relatively less studied class of compounds, primarily due to the presence of light elements, which result in high thermal conductivity and inherent stability problems. In this work, we present a stable phosphide-tetrahedrite, Ag6Ge10P12, which possesses the highest zT (∼0.7) among all known phosphides at intermediate temperatures (750 K). We examine the intrinsic electronic and thermal transport properties of this compound by expressing the transport properties in terms of weighted mobility (μW), transport coefficient (σE0), and material quality factor (B), from which we are able to elucidate that the origin of its high zT can be attributed to the platelike Fermi surface and high level of band multiplicity related to its complex band structure. Finally, we discuss the origin of the low lattice thermal conductivity observed in this compound using experimental sound velocity, elastic properties, and Debye-Callaway model, thus laying the foundation for similar stable phosphides as potentially earth-abundant and nontoxic intermediate-temperature thermoelectric materials.

GeTe is highly sought-after due to its versatility as high-performance thermoelectrics, phase change materials, as well as ferroelectric Rashba semiconductor. Compared to most thermoelectric materials, it has an additional degree of freedom of rhombohedral-cubic phase transition at 673 K. At this temperature, the lattice thermal conductivity approaches theoretical minimum due to ferroelectric instability while the high-energy Σ and low-energy L bands converge to give outstanding electronic properties. Therefore, modulation of the phase transition temperature allows simultaneous and synergistic tuning of electronic and thermal transport properties to achieve high zT. In this work, Sn alloying together with Bi, Sb doping is used to suppress the phase transition to achieve a pure cubic structure with lattice thermal conductivity of around 0.4 W/mK and peak zT of 1.7 at 723 K with average zT of 1.23 between 400 and 800 K. Furthermore, Vickers hardness of 270, and Young’s modulus of 63.5 GPa in Ge0.4Sn0.4Bi0.02Sb0.12Te is by far the highest amongst binary chalcogenides. More importantly, the high quality factor achieved in this work enables ample room for further zT improvements. The fundamental insights drawn from this work provide a pathway towards engineering GeTe-based alloys to achieve high zT at any temperature of interest. Agency for Science, Technology and Research (A*STAR) Ministry of Education (MOE) Accepted version

A new kind of cationic brush-like terpolymer was synthesized by copper(I)-mediated atom transfer radical polymerization (ATRP) of methyl ether poly(ethylene glycol) methacrylate (mPEGMA), poly(propylene glycol) methacrylate (PPGMA) and dimethylaminoethyl methacrylate (DMAEMA) in the presence of ethyl α-bromoisobutyrate as ATRP initiator. The poly(PEG/PPG/DMAEMA) terpolymer was featured with a cationic backbone containing PDMAEMA segments and amphiphilic side chains composed of hydrophilic PEG and hydrophobic PPG short branches. The copolymer was characterized by 1H NMR, Fourier transform IR and gel permeation chromatography. The thickening behavior of this copolymer in a surfactant system (sodium dodecyl sulfate, SDS) was extensively investigated by a rheological study. It was found that the copolymer can effectively thicken the SDS surfactant system at low concentrations of both copolymer and surfactant. More interestingly, the thickened SDS system by this copolymer showed dramatic pH responsive rheological behavior in the pH range 4–10. Thus the rheological behavior of the thickened SDS system was tunable by pH value. Based on our findings, a novel thickening mechanism is proposed for this kind of cationic brush-like terpolymer. This kind of cationic brush-like copolymer would be a new type of rheology modifier for advanced hair/skin care systems. © 2014 Society of Chemical Industry

In this work, spherical mesoporous silica nanospheres (MSNs) functionalized by content-tunable amino groups were synthesized via a facile co-condensation method aided by both ionic and nonionic surfactants. 3-Aminopropyltrimethoxysilane (APTMS) was added to co-condense with tetraethyl orthosilicate in basic aqueous solution at varied concentration, obtaining different surface amino content. The influence of APTMS concentration on the morphology, pore structure and surface amino coverage of synthesized nanoparticles was systematically investigated. A decelerating trend of the “surface amino coverage” growing with increasing “APTMS concentration” was observed, indicating there is a maximum grafting limit for APTMS on the exterior MSN surface. For the first time, MSN containing amino group (NH 2 -MSN) was utilized as inorganic nanofiller in polyamide-6 (PA6) nanocomposites, prepared by incorporating NH 2 -MSN and organo-montmorillonite (OMMT) simultaneously in PA6 through melt compounding. Mechanical properties of PA6 nanocomposites were fully investigated at two widely varied strain-rates (quasi-static and high-speed). The PA6/NH 2 -MSN/OMMT ternary nanocomposite showed simultaneous improvement of tensile stiffness (Young’s modulus and maximum tensile stress) and ductility (elongation at break). PA6-MSN interface analysis indicated that the strong interfacial affinity (covalent binding) may confine the mobility of PA6 molecules along the tension axis and obstruct the growing/propagation of micro-cracks. However, the synergistic effect involving nanofillers of different shape (spherical NH 2 -MSN and platelet OMMT) was considered to play critical role for the uniquely improved tensile ductility of ternary nanocomposite.

New biodegradable and thermoresponsive amphiphilic multiblock poly(ester urethane) copolymers consisting of poly(1,4-butylene adipate) (PBA), poly(ethylene glycol) (PEG), and poly(propylene glycol) (PPG) were synthesized. The chemical structures and molecular characteristics of the copolymers were confirmed by gel permeation chromatography and proton nuclear magnetic resonance spectroscopy. The copolymers had relatively high molecular weights ranging from 40k to 46k with narrow molecular weight distributions. The amphiphilic block copolymers could form micelles in water with very low critical micellization concentration (CMC) values that are dependent on the PBA content and temperature. The copolymers with higher PBA contents showed lower CMC values because the PBA segments increased the hydrophobicity of the copolymers. The thermodynamic parameters of the micellization process were studied through CMC dependence on temperature, and it was concluded that the micellization process is a spontaneous and entropy-driven process. The aqueous solutions of the copolymers could form thermosensitive hydrogels with very low critical gelation concentrations (CGCs) ranging from 5 to 8 wt%. Higher PBA contents resulted in lower CGCs and higher strength of the hydrogels, again because of the hydrophobicity of the PBA segments. The hydrolytic degradation studies showed that these hydrogels could degrade rapidly within a period of 40 days, which resulted in the mass loss of the hydrogels and the molecular weight decrease of the copolymers. The copolymer hydrogels could sustain the release of the bovine serum albumin (BSA) model protein drug up to a few weeks, and the protein release rate could be controlled by the PBA contents in the copolymers. The cell viability assay showed that the poly(PEG/PPG/PBA urethane)s did not elicit cytotoxic response against the L929 cells with the copolymer concentration up to 0.63 mg mL−1. The PBA-based polyurethane copolymers may be candidate biomaterials for promising biomedical applications.

This paper reports the synthesis and characterization of new hyperbranched amphiphilic polyurethane multiblock copolymers consisting of poly(propylene glycol) (PPG), poly(ethylene glycol) (PEG), and polycaprolactone (PCL) segments as in situ thermogels. The hyperbranched poly(PPG/PEG/PCL urethane)s, termed as HBPEC copolymers, were synthesized from PPG-diol, PEG-diol, and PCL-triol by using 1,6-hexamethylene diisocyanate (HMDI) as a coupling agent. The compositions and structures of HBPEC copolymers were determined by GPC and 1H NMR spectroscopy. We carried out comparative studies of the new hyperbranched copolymers with their linear counterparts, the linear poly(PPG/PEG/PCL urethane) (LPEC) copolymer and Pluronic F127 PEG-PPG-PEG block copolymer, in terms of their self-assembly and aggregation behaviors and thermoresponsive properties. HBPEC copolymers were found to show thermoresponsive micelle formation and aggregation behaviors. Particularly, the lower critical solution temperature (LCST) of the copolymers was significantly affected by the copolymer architecture. HBPEC copolymers showed much lower LCST than LPEC, the linear counterpart. Our studies revealed that the effect of hyperbranch architecture was more prominent in the gelation of the copolymers. The aqueous solutions of HBPEC copolymers exhibited thermogelling behaviors at critical gelation concentrations (CGCs) ranging from 4.3 to 7.4 wt %. These values are much lower than those reported on other PCL-contained linear thermogelling copolymers and Pluronic F127 copolymer. In addition, the CGC of HBPEC copolymers is much lower than the control LPEC copolymer. More interestingly, at high temperatures, while LPEC and other linear thermogelling copolymers formed turbid sol, HBPEC formed a dehydrated gel. Our data suggest that these phenomena are caused by the hyperbranched structure of HBPEC copolymers, which could increase the interaction of copolymer branches and enhance the chain association through synergetic hydrogen bonding effect. The thermogelling behavior of HBPEC block copolymers was further evidenced by the 1H NMR molecular dynamic study and rheological study, which further support the above hypothesis. The hydrolytic degradation study showed that the HBPEC copolymer hydrogels are biodegradable under physiological conditions. Together with the good cell biocompatibility demonstrated by the cytotoxicity study, the new thermogelling copolymers reported in this paper could potentially be used as in situ-forming hydrogels for biomedical applications.

A series of novel polypseudorotaxanes, in which multiple α-cyclodextrin (α-CD) and γ-cyclodextrin (γ-CD) rings were randomly co-threaded over a poly[(ethylene oxide)-ran-(propylene oxide)] (P(EO-r-PO)) copolymer chain, were prepared by reacting the copolymer simultaneously with α-CD and γ-CD in aqueous solution. X-ray diffraction studies demonstrated that both α-CD and γ-CD molecules in the inclusion complexes (ICs) assumed a channel-type structure. 1H NMR spectra revealed that the compositions of the polypseudorotaxanes were strongly dependent on the molar ratio between α-CD and γ-CD in the feed. More interestingly, when we used the moderately bulk 2,4,6-trinitrophenyl (TNP) group, which is larger than the cavity of α-CD but smaller than that of γ-CD, to cap the two ends of the polypseudorotaxanes, we obtained polyrotaxanes with both α-CD and γ-CD randomly co-threaded over the P(EO-r-PO) chain, but the compositions of the polyrotaxanes were different from the corresponding polypseudorotaxanes because some γ-CD rings dethreaded since the cavity of γ-CD is larger than TNP. However, some γ-CD rings were sandwiched by α-CD rings, and these γ-CD and α-CD rings were both entrapped over the P(EO-r-PO) chain by the TNP ends. Our results revealed that how the compositions of the polypseudorotaxanes and the polyrotaxanes were different, and how their compositions were affected by the feed ratio between α-CD and γ-CD.

New polyrotaxanes, in which multiple α-cyclodextrin (α-CD) rings were threaded and imprisoned on a reverse Pluronic PPO–PEO–PPO triblock copolymer chain and capped by two 2,4-dinitrophenyl groups at the two ends, were synthesized based on the block-selected inclusion complexation between the PPO–PEO–PPO triblock copolymers and α-CD. The polyrotaxanes were isolated and purified through size exclusion chromatography, and the chromatograms showed that the polyrotaxanes had high molecular masses as compared with their respective components. The polyrotaxanes were further characterized by using 13C and 1H 1D and 2D NMR spectroscopy, wide-angle X-ray diffraction, thermogravimetric analysis, and differential scanning calorimetry. It was found that the threading PPO–PEO–PPO triblock copolymers became more thermally stable because they were complexed by the imprisoned α-CD. The studies demonstrated that the numbers of α-CD rings imprisoned in the polyrotaxanes were directly related to the PEO block length, rather than to the PPO block length. In all the three polyrotaxanes synthesized in this work, the central PEO block was fully covered and complexed by α-CD stoichiometrically, while the flanking PPO bocks remained free and uncomplexed. Therefore, the new polyrotaxanes took a PPO-polyrotaxane-PPO triblock architecture. The polyrotaxanes with such block architecture may be interesting supramolecular precursor for designing novel functional materials.

This article reports a detailed study on the hydrogel formation of poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) (PEO-PPO-PEO) triblock copolymers with alpha-cyclodextrin (alpha-CD) in aqueous solutions. The gelation kinetics and the gel rheological properties were studied using viscometry. The sol-gel phase transitions were studied using phase diagrams, while the gelation mechanism was studied using differential scanning calorimetric analysis. It was concluded that the gelation was induced by the complex formation between the PEO segments of the PEO-PPO-PEO triblock copolymer and alpha-CD, and the further self-assembly of the partially formed inclusion complexes. The addition of alpha-CD largely reduced the concentration of the copolymer needed for gel formation. The gels were thixotropic and reversible, and potentially suitable for use as an injectable drug-delivery system.

Hydrolytic degradable PBT/PEG copolymer was synthesized by macromolecular transesterification method from PBT and PEG macromonomers. The resultant copolymers were characterized by (1)H-NMR and GPC. The non-isothermal crystallization behavior of these copolymers was studied by differential scanning calorimetry (DSC). The water absorption and hydrolytic degradation behavior of PBT/PEG copolymers were also studied in detail.

A materials design of a new supramolecular hydrogel self-assembled between alpha-cyclodextrin and a biodegradable poly(ethylene oxide)-poly[(r)-3-hydroxybutyrate]-poly(ethylene oxide) (PEO-PHB-PEO) triblock copolymer was demonstrated. The cooperation effect of complexation of PEO segments with alpha-cyclodextrin and the hydrophobic interaction between PHB blocks resulted in the formation of the supramolecular hydrogel with a strong macromolecular network. The in vitro release kinetics studies of fluorescein isothiocyanate labeled dextran (dextran-FITC) model drug from the hydrogel showed that the hydrogel was suitable for relatively long-term sustained controlled release of macromolecular drugs, which many simple triblock copolymer hydrogel systems could not achieve. The hydrogel was found to be thixotropic and reversible, and can be applied as a promising injectable drug delivery system.

The self-aggregation behavior of two amphiphilic poly(ethylene oxide)-poly[(R)-3-hydroxybutyrate]-poly(ethylene oxide) (PEO-PHB-PEO) triblock copolymer samples with nearly identical PHB block lengths but different PEO block lengths, PEO-PHB-PEO(2000-810-2000) and PEO-PHB-PEO(5000-780-5000), was studied with dynamic and static light scattering (DLS and SLS), in combination with fluorescence spectroscopy and transmission electron microscopy (TEM). The formation of polymeric micelles by the two PEO-PHB-PEO triblock copolymers was confirmed with fluorescence technique and TEM. DLS analysis showed that the hydrodynamic radius (R(h)) of the monodistributed polymeric micelles increased with an increase in PEO block length. The relative thermostability of the triblock copolymer micelles was studied by SLS and DLS at different temperatures. The aggregation number and the ratio of the radius of gyration over hydrodynamic radius were found to be independent of temperature, probably due to the strong hydrophobicity of the PHB block. The combination of DLS and SLS studies indicated that the polymeric micelles were composed of a densely packed core of hydrophobic PHB blocks and a corona shell formed by hydrophilic PEO blocks. The aggregation numbers were found to be approximately 53 for PEO-PHB-PEO(2000-810-2000) micelles and approximately 37 for PEO-PHB-PEO(5000-780-5000) micelles. The morphology of PEO-PHB-PEO spherical micelles determined by DLS and SLS measurements was further confirmed by TEM.

Of many polymeric biomaterials, hydrogels are of special importance because of their favorable biocompatibility and pertinence in delivering delicate bioactive agents such as proteins. Physical hydrogels have attracted much attention for controlled drug delivery because of the mild and aqueous conditions involved in trapping bioactive agents. This paper reviews our recent progress on developing a new class of physical hydrogels based on the supramolecular self-assembly between cyclodextrins and bioabsorbable poly(ethylene oxide) (PEO) or its copolymers. Being thixotropic, the hydrogels can be injected through needles and applied as injectable drug delivery systems. The properties of the hydrogels also can be fine-tuned with triblock copolymers where PEO segments flank hydrophobic or biodegradable segments in the middle.

Polymeric hydrogels long have attracted interest for biomaterials applications because of their generally favorable biocompatibility. High in water content, they are particularly attractive for delivery of delicate bioactive agents, such as proteins. However, because they require covalent crosslinking for gelation, many hydrogels can be applied only as implantables, and incorporation of drugs by sorption may be time-consuming and limiting with regard to the loading level. Therefore a delivery formulation where gelation and drug loading can be achieved simultaneously, taking place in an aqueous environment and without covalent crosslinking, would be attractive. Herein is described a new class of injectable and bioabsorbable supramolecular hydrogels formed from poly(ethylene oxide)s (PEOs) and α-cyclodextrin (α-CD) for controlled drug delivery. The hydrogel formation is based on physical crosslinking induced by supramolecular self-assembling with no chemical crosslinking reagent involved. The supramolecular structure of the hydrogels was confirmed with wide-angle X-ray diffraction studies. The gelation kinetics was found to be dependent on the concentrations of the polymer and α-CD as well as on the molecular weight of the PEO used. The rheologic studies of the hydrogels showed that the hydrogels were thixotropic and reversible and that they could be injected through fine needles. The components of the supramolecular hydrogels potentially are biocompatible and nontoxic. Drugs can be encapsulated directly into the hydrogels in situ at room temperature without any contact with organic solvents. The supramolecular hydrogels were evaluated in terms of their in vitro release kinetics. The rate-controlling mechanism of macromolecular drug release might be the erosion of the hydrogels. © 2003 Wiley Periodicals, Inc. J Biomed Mater Res 65A: 196–202, 2003

New biodegradable amphiphilic ABA triblock copolymers consisting of poly(ethylene oxide) (PEO) as the hydrophilic block and poly[(R)-3-hydroxy butyrate] (PHB) as the hydrophobic block were synthesized by coupling two chains of methoxy-PEO-monocarboxylic acid with a low molecular weight telechelic hydroxylated PHB (PHB-diol) chain in the middle. The PHB-diol was prepared from high molecular weight natural source PHB by transesterification reaction with diethylene glycol. The target triblock copolymers were isolated and purified from the reaction mixtures through repeated precipitation and fractionation. The structures and molecular characteristics of the PEO−PHB−PEO triblock copolymers were studied by GPC, 1H NMR, and FT-IR. All of the triblock copolymers had unimodal peaks in the GPC chromatographs. The chain architecture of the triblock copolymers was confirmed by the 1H NMR spectra. A combination of GPC and 1H NMR analysis determined the lengths of the PEO and PHB blocks of the copolymers. The thermal p...

A series of new polypseudorotaxanes were synthesized in high yields when the middle poly(ethylene oxide) (PEO) block of poly(propylene oxide)-poly(ethylene oxide)-poly(propylene oxide) (PPO-PEO-PPO) triblock copolymers was selectively recognized and included by alpha-cyclodextrin (alpha-CD) to form crystalline inclusion complexes (ICs), although the middle PEO block was flanked by two thicker PPO blocks, and a PPO chain had been previously thought to be impenetrable to alpha-CD. X-ray diffraction studies demonstrated that the IC domains of the polypseudorotaxanes assumed a channel-type structure similar to the necklace-like ICs formed by alpha-CD and PEO homopolymers. Solid-state CP/MAS (13)C NMR studies showed that the alpha-CD molecules in the polypseudorotaxanes adopted a symmetrical conformation due to the formation of ICs. The compositions and stoichiometry of the polypseudorotaxanes were studied using (1)H NMR, and a 2:1 (ethylene oxide unit to alpha-CD) stoichiometry was found for all polypseudorotaxanes although the PPO-PEO-PPO triblock copolymers had different compositions and block lengths, suggesting that only the PEO block was closely included by alpha-CD molecules, whereas the PPO blocks were uncovered. The hypothesis was further supported by the differential scanning calorimetry (DSC) studies of the polypseudorotaxanes. The glass transitions of the PPO blocks in the polypseudorotaxanes were clearly observed because they were uncovered by alpha-CD and remained amorphous, whereas the glass-transition temperatures increased, because the molecular motion of the PPO blocks was restricted by the hard crystalline phases of the IC domains formed by alpha-CD and the PEO blocks. The thermogravimetric analysis (TGA) revealed that the polypseudorotaxanes had better thermal stability than their free components due to the inclusion complexation. Finally, the kinetics of the threading process of alpha-CD onto the copolymers was also studied. The findings reported in this article suggested interesting possibilities in designing other cyclodextrin ICs and polypseudorotaxanes with block structures.

The miscibility of polysulfone (PSf) and poly(ether sulfone) (PES) with three tertiary amide polymers has been studied. PES is miscible with poly(N-methyl-N-vinylacetamide) (PMVAc) and with poly(N,N-dimethylacrylamide) (PDMA) but not with poly(2-methyl-2-oxazoline) (PMOx). Miscible PES/PDMA blends show lower critical solution temperature behavior. However, PSf is immiscible with all the three tertiary amide polymers. Previous studies have shown that both PES and PSf are miscible with poly(N-vinyl-2-pyrrolidone). PES is also miscible with poly(2-ethyl-2-oxazoline) but PSf is not. Therefore, PES is more readily miscible with tertiary amide polymers as compared to PSf.

The phase behaviour of blends of four poly(chlorinated-ethyl methacrylates) with poly(styrene-co-acrylonitrile) (SAN) and with poly(p-methylstyrene-co-acrylonitrile) (pMSAN) was studied. Poly(1-chloroethyl methacrylate) and poly(2,2-dichloroethyl methacrylate) are miscible with SAN and pMSAN over a certain copolymer composition range, showing miscibility windows. Poly(2,2,2-trichloroethyl methacrylate) (PTCEMA) is miscible with SAN and pMSAN having high acrylonitrile contents, showing miscibility doors. PTCEMA is also miscible with polyacrylonitrile. However, poly(1,2,2,2-tetrachloroethyl methacrylate) is immiscible with any of the SAN and pMSAN samples.

Silver nanoparticles have been prepared by photoreduction of silver nitrate with 254 nm UV light in the presence of poly(N-vinylpyrrolidone). The effects of PVP concentration on the particle size, the UV−vis absorption peak, and the rate of the photoreduction process were studied. The average particle size ranged from 15.2 to 22.4 nm, with the corresponding UV−vis absorption peak position at 404−418 nm in 1−0.25 wt % PVP. The rate of the photoreduction process was observed to increase with the PVP concentration. X-ray photoelectron spectroscopic studies further revealed that the polymer interacts with silver particles through the oxygen atom in the >CO group. A negative shift of binding energy in the Ag 3d5/2 for silver nanoparticles was observed.

The miscibility of a ternary system of poly(3-hydroxybutyrate), poly(ethylene oxide) and polyepichlorohydrin was studied by differential scanning calorimetry. The three binary blend systems are individually miscible. All the ternary blends were found to be miscible as shown by the existence of a single glass transition temperature in each blend. The interaction parameters of the three binary pairs are of similar magnitude and do not lead to a “Δχ” effect.

Di-block co-polymers of poly(ethylene glycol)-poly(L-lactic acid) (PEG-PLLA) were prepared by ring-opening polymerization, and their self-association and micelle formation were investigated. The block co-polymers have the same block length of the hydrophilic PEG segment (Mn = 2000), but different chain lengths of the hydrophobic PLLA segment (Mn = 700, 1000 and 1300, respectively). The di-block co-polymers synthesized were characterized by GPC, 1H-NMR, TGA and DSC. The critical micelle concentration (CMC) of the PEG-PLLA micelles was determined at various temperatures (5-45 degrees C) using a dye absorption technique involving fluorescence spectrophotometry with pyrene as a probe to monitor the change in the polarity of the microenvironment in the micelle. An increase in the molecular weight of the hydrophobic block decreases the CMC. The partition coefficients of pyrene between the micellar and aqueous phases range from 0.68 x 10(4 )to 1.76 x 10(4), depending on the PLLA content in the block co-polymers. An Arrhenius plot of ln(CMC) versus 1/T exhibited an almost constant CMC at low temperatures (35 degrees C), followed by an increase of the CMC at higher temperatures (35 degrees C). The increase of the CMC with temperature indicates the increase of the mobility of the hydrophobic PLLA core. These results were confirmed by 1H-NMR measurements. The micelle size and size distribution were determined by dynamic light scattering (DLS), and were in the range of 78-92 nm. A spherical micelle shape was confirmed by transmission electron microscopy. These results indicate that the CMC and the thermal characteristics of the core-forming segment of the block co-polymer play an important role in the properties of the polymer micelles used for drug delivery.

This paper reports the studies on micelle formation of new biodegradable amphiphilic poly(ethylene oxide)-poly[(R)-3-hydroxybutyrate]-poly(ethylene oxide) (PEO-PHB-PEO) triblock copolymer with various PHB and PEO block lengths in aqueous solution. Transmission electron microscopy showed that the micelles took an approximately spherical shape with the surrounding diffuse outer shell formed by hydrophilic PEO blocks. The size distribution of the micelles formed by one triblock copolymer was demonstrated by dynamic light scattering technique. The critical micellization phenomena of the copolymers were extensively studied using the pyrene fluorescence dye absorption technique, and the (0,0) band changes of pyrene excitation spectra were used as a probe for the studies. For the copolymers studied in this report, the critical micelle concentrations ranged from 1.3 x 10(-5) to 1.1 x 10(-3) g/mL. For the same PEO block length of 5000, the critical micelle concentrations decreased with an increase in PHB block length, and the change was more significant in the short PHB range. It was found that the micelle formation of the biodegradable amphiphilic triblock copolymers consisting of poly(beta-hydroxyalkanoic acid) and PEO was relatively temperature-insensitive, which is quite different from their counterparts consisting of poly(alpha-hydroxyalkanoic acid) and PEO.

In this paper, we demonstrate a simple and practical method to prepare chemically crosslinked gelatin-based hydrogels using β-cyclodextrin (β-CD) that plays a dual role as a crosslinker as well as a host molecule for enhanced binding of anticancer drug methotrexate (MTX), to achieve high drug loading level as well as controlled and sustained release of the anticancer drug. For this purpose, a series of novel β-CD-crosslinked gelatin-based hydrogels were synthesized and characterized. The β-CD content of the hydrogels was 11–15%, and the crosslinking degree was 21–36%. The gelatin-based hydrogels could swell well in PBS buffer. The hydrogels degraded hydrolytically and the degradation was accelerated by collagenase in PBS buffer. It was found that the higher water content resulted in faster biodegradation of the hydrogels regardless of the crosslinker used. Pyrene was used as a fluorescence probe to investigate the micro-environment of the gelatin-based hydrogels. Pyrene was well adsorbed in the β-CD-crosslinked hydrogels, and the pyrene molecules in the hydrogels were included and complexed within the hydrophobic cavities of the β-CD crosslinkers. The adsorption, loading, binding and complexation, and release of MTX in or from the hydrogels were investigated. MTX was adsorbed and loaded into the hydrogels by immersing the swollen hydrogel samples in MTX saturated aqueous solution. The loading of MTX in the hydrogels was confirmed by measuring the UV-vis spectra of the MTX-loaded hydrogels, the spectra indicated that the loaded MTX was complexed by β-CD in the β-CD-crosslinked hydrogels. Our data showed that the complexation of MTX with β-CD crosslinkers largely increased the loading level of MTX in the hydrogels. The complexation could also reduce the initial burst release effect, and then retard the release of the complexed MTX for a certain period, until the hydrogels started to hydrolytically degrade and all remained MTX was released. Due to the unique structures and properties, the β-CD-crosslinked gelatin-based hydrogels demonstrated an interesting multiphasic profile for controlled and sustained release of the MTX drug. Thus, the β-CD-crosslinked gelatin-based hydrogels may be utilized as a promising drug carrier for controlled and sustained release and localized delivery of anticancer drugs.

Novel supramolecular hydrogels were formed between pyrene-terminated poly(ethylene glycol) star polymers and γ-cyclodextrin (γ-CD), through the inclusion complexation of dimers of the pyrene terminals with γ-CD, where γ-CD was directly used as a supramolecular cross-linking reagent without any modification.

A series of new thermosensitive polyurethane copolymers composed of heptakis(2,6-di-O-methyl)-β-cyclodextrin (DM-β-CD), poly(propylene glycol) (PPG), and poly(ethylene glycol) (PEG) blocks using 1,6-hexamethylene diisocyanate (HMDI) as a coupling agent were synthesized. Their chemical structures and molecular characteristics were studied using GPC analysis and 1H NMR and 13C NMR spectral analysis. We found that the copolymers had high molecular weight and the DM-β-CD, PPG, and PEG blocks were bonded by a hexamethylene dicarbamyl (HMDC) junction. DSC analysis showed that the molar motion of the PPG and PEG segments was restricted in the copolymers. Moreover, the copolymers are amphiphilic and they have very low critical micelle concentration (CMC) values ranging from 2.63–8.51 g L−1. Upon increasing temperature, the aqueous solutions of the copolymers were found to undergo a reversible clear sol–gel–turbid sol transition. The results from phase diagrams showed that the copolymers had very low critical gelation concentration (CGC) values ranging within 3–6 wt%. The copolymers synthesized in the study are easily soluble in water at room temperature, thus hydrophobic pharmaceutical agents could be entrapped into the hydrophobic cavity of CDs or loaded in the core of micelles. Then, these pharmaceutical agents are encapsulated into the gel when the copolymer forms a gel depot at around body temperature. Hence, these copolymers have potential to be used as injectable drug delivery systems.