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Mark–Houwink parameters are determined for sodium alginate with low (SA LV) and medium (SA MV) molecular mass via a rheological approach. Firstly, salt screening concentration and polyelectrolyte nature of the polymers are investigated. Despite both alginates behaving as neutral polymer in θ solvent, differences are observed between them with the strong associative nature of SA MV highlighted by an abnormal high viscosity concentration dependence compared with the predicted values. The polysaccharide-specific hydrodynamic volume (i.e., intrinsic viscosity) is determined via Fedors approach, which is proved to provide accurate results applicable to a wide concentration range. A viscosity–molecular mass–concentration relationship is finally derived to calculate Mark–Houwink parameters via a non-linear regression according to Kulicke equation; the obtained values are consistent with those reported in literature, confirming the semi-flexible nature of SA in the investigated environment and proving the effectiveness of the proposed approach for polyelectrolytes with added salt ions.

The present review discusses the use of cyclodextrins and their derivatives to prepare electrospun nanofibers with specific features. Cyclodextrins, owing to their unique capability to form inclusion complexes with hydrophobic and volatile molecules, can indeed facilitate the encapsulation of bioactive compounds in electrospun nanofibers allowing fast-dissolving products for food, biomedical, and pharmaceutical purposes, filtering materials for wastewater and air purification, as well as a variety of other technological applications. Additionally, cyclodextrins can improve the processability of naturally occurring biopolymers helping the fabrication of "green" materials with a strong industrial relevance. Hence, this review provides a comprehensive state-of-the-art of different cyclodextrins-based nanofibers including those made of pure cyclodextrins, of polycyclodextrins, and those made of natural biopolymer functionalized with cyclodextrins. To this end, the advantages and disadvantages of such approaches and their possible applications are investigated along with the current limitations in the exploitation of electrospinning at the industrial level.

Alginate-based electrospun nanofibers prepared via electrospinning technique represent a class of materials with promising applications in the biomedical and pharmaceutical industries. However, to date, the effect of alginate molecular mass and block composition on the biological response of such systems remains to some extent unclear. As such, in the present work, three alginates (i.e., M.pyr, L.hyp, A.nod) with different molecular features are employed to prepare nanofibers whose ability to promote cell adhesion is explored by using both skin and bone cell lines. Initially, a preliminary investigation of the raw materials is carried out via rheological and zeta-potential measurements to determine the different grade of polyelectrolyte behaviour of the alginate samples. Specifically, both the molecular mass and block composition are found to be important factors affecting the alginate response, with long chains and a predominance of guluronic moieties leading to a marked polyelectrolyte nature (i.e., lower dependence of the solution viscosity upon the polymer concentration). Subsequently, physically crosslinked alginate nanofibrous mats are first morphologically characterized via both scanning electron and atomic force microscopy, which show a homogenous and defect-free structure, and their biological response is then evaluated. Noticeably, fibroblast and keratinocyte cell lines do not show significant differences in terms of cell adhesion on the three mats (i.e., 30-40% and 10-20% with respect to the seeded cells, respectively), with the formers presenting a greater affinity toward the alginate-based nanofibers. Conversely, both the investigated osteoblast cells are characterized by a distinct behaviour depending on the alginate type. Specifically, polysaccharide samples with an evident polyelectrolyte nature are found to better promote cell viability (i.e., cell adhesion in the range 15-36% with respect to seeded cells) compared to the ones displaying a nearly neutral behaviour (i.e., cell adhesion in the range 5-25% with respect to seeded cells). Therefore, the obtained results, despite being preliminary, suggest that the alginate type (i.e., molecular structure properties) may play a topical role in conditioning the efficiency of healing patches for bone reparation, but it has a negligible effect in the case of skin regeneration.

Due to its high toxicity, Pb2+ pollution is a serious threat for human health and environments. However, in situ real-time detection of Pb2+ pollution is difficult and laboratory instruments are usually required. Then, the possibility to monitor water quality without laboratory instruments could lead to the extensive assessment of polluted water sources, especially in rural environments and developing countries where large lead concentrations are often found in surface water. Consequently, new simple colorimetric sensors are highly interesting in the field. In this work we report for the first time disposable polymer planar 1D photonic crystals made of poly (N-vinylcarbazole) as high refractive index medium and sodium alginate as low refractive index and active medium for the detection of Pb2+ in water. The detection relies on the ionic exchange occurring into the alginate matrix. This process effectively induces a physical cross-linking phenomenon, which inhibits water solubilization of the polymer. In turn, this affects the spectral response of the planar 1D photonic crystals modifying its color.

In the present work, different sodium alginates were used to prepare nanofibrous mats by means of electrospinning technique. Firstly, a molecular characterization of each sample was carried out: the molecular mass and the composition, i.e. mannuronic/guluronic acid ratio, were determined using the Mark–Houwink–Sakurada relation and FTIR spectroscopy, respectively. Afterwards, the polyelectrolyte nature and the characteristic concentration regimes of each alginate were studied through rheological tests. The results indicated that both the molecular mass and the composition strongly influence the properties of the polymer in solution; in particular, long chains and the predominance of guluronic moiety lead to a marked polyelectrolyte behaviour. Subsequently, in order to obtain a good spinnability, polyethylene oxide and Triton X-100 were added to alginate-based solutions. The resulting solutions were carefully characterized by a rheological point of view; the viscosity, viscoelasticity, thixotropy and thermal stability were investigated and correlated with their capability of being electrospun. Two different set-ups were used for electrospinning: one consisted in a dry collector and the other one in a wet collector (immersed in a collecting solution). The morphology of the membranes was characterized through scanning electron microscopy; moreover, thermogravimetric analysis was performed in order to study the final composition and the thermal degradation. The preliminary results indicated that the membrane obtained using guluronic-rich alginate and the wet-collector system is composed of only sodium alginate and characterized by thin fibres and a high porosity, which could make it suitable for pharmaceutical and biomedical applications.

The molecular mass of two sodium alginates with the same composition but different chain length is reduced via a simple ultrasonic treatment and monitored by rheological measurements. The polymer molecular mass decreases until a lower limiting value of 100 kg/mol is reached, with the degradation occurring via a mid-point-chain kinetic consisting into the breakage of the glycosidic bonds towards the middle of the macromolecules. The evaluation of the concentration regimes (i.e. viscosity dependence upon the polymer concentration) demonstrates that short chains are characterized by higher critical concentrations and lower scaling factors, most likely owing to their poor ability to form entanglements. Nevertheless, the typical behaviour of neutral polymer in θ solvent is observed independently of the alginate molecular mass. The viscosity temperature dependence of the investigated solutions obeys Arrhenius law in a wide temperature range. Additionally, the flow activation energy is observed to follow a linear relationship with the polymer molecular mass with values of 26.2 kJ/mol for the longest chains and 18.2 kJ/mol for the shortest ones. Consequently, ultrasonic treatment is here proved to be extremely efficient to reduce the molecular mass of alginate, thus representing a fast, safe and cost-effective approach to obtain materials with tailored properties.

Agar is a natural polymer commonly used in various fields of application ranging from cosmetics to the food industry. In particular, for over forty years agar gels have been used in the field of conservation of Cultural Heritage where they are considered as one of the main well-performing tools in cleaning procedures. In the present work, the relation between the chemical composition and the mechanical strength of four different agar hydrogels was evaluated by comparing the results obtained via pyrolysis-gas chromatography/mass spectrometry and rheological characterization. Agar composition was studied by means of a pyrolysis-gas chromatography/mass spectrometry approach in order to differentiate the anhydrous, galactose and glucose units. Pristine agar gels, gels after double annealing, and gels with and without chelating agent were studied by means of amplitude, frequency and time sweep rheological tests to evaluate all the preparation approaches commonly used by conservators, also taking into account changes in the transparency via UV–vis spectroscopy. A high percentage of anhydrous units in the polymer backbone was found to provide superior mechanical stiffness to the pristine hydrogels, even if it did not seem to affect their long-term stability. The annealing process significantly improved the rheological response of galactose-rich agar hydrogels being able to promote the establishment of additional crosslinking points, whereas the additive presence showed to improve the hydrogel stiffness owing to a more structured polymer network. Moreover, the progressive reduction of the impurities and/or network defects within the hydrogels occurring due to the annealing process slightly increased the transparency of the hydrogels, which is an important aspect for applications in the conservation of Cultural Heritage.

Hyaluronic acid (HA) solutions represent an important class of biomedical products, mostly used in viscosupplementation of joints and as fillers. In the present work the hydrodynamic and rheological properties of hyaluronic acid, of differing MW(90-4000 kDa), in physiological saline were investigated. Firstly, the effective conformation taken by the polymer chains was studied using dynamic light scattering. It was observed that they behaved like random coils which dimension is higher increasing the molecular weight of the material. Secondly, combining a novel microrheological technique, based on the dynamic light scattering of tracer particles, with conventional rheometry, it was possible to study in which way the molecular weight and the concentration of the polymer influence the storage modulus (G’), loss modulus (G”) and complex viscosity (η*) of its solutions, over an extended frequency range (typically 0.01-10000 Hz). This extended characterization allowed determination of the mesh size ξ of the physical network, created by the entangled polymer chains. Calculated mesh sizes in the range 200-700 nm were observed, demonstrating the possibility to use these systems as injectable carriers of biomolecules with an appropriate dimension.

To verify the effect of hydrogen bonding on the polymer mixing, blends of poly(vinyl methyl ether) (PVME) and poly(methyl methacrylate) (PMMA) with poly(4-hydroxy styrene) (PHS), respectively, have been prepared. The effect of hydrogen bond strength on the enthalpy of mixing, ΔHM, was investigated by microcalorimetric measurements and FTIR spectroscopy. Infrared analysis allowed to measure the amount of hydrogen bonding by a curve fitting procedure in PHS/PMMA blends, looking to the change in the characteristic bands of carbonyl group of PMMA. In the case of PHS/PMVE, the hydroxyl-stretching region has been investigated to have only a qualitative estimation of hydrogen bonding. For both PHS/PMVE and PHS/PMMA systems, the measured exothermic (negative) ΔHM decreases with the increase in the PHS content, indicating that the presence of strong specific intermolecular interactions, such as hydrogen bonding, favours the polymer blending.

Porous membranes based on polydimethylsiloxane fibers with titanium dioxide nanoparticles were developed to be used as photocatalysts. PDMS was chosen as a support for the titania because of its high thermal and chemical resistance to the photodegradative effect of the TiO2. Porous membranes are produced via electrospinning using three different apparatus configurations. The photocatalytic activity analysis shows that the best results are obtained dispersing the titanium oxide on the surface of the polymer using an electrospinning configuration which involves the use of two needles. The membranes produced in this way show a good catalytic activity, even though lower than the one observed for the pure TiO2 nanoparticles. This is caused by the low wettability of the membranes and by the surface area of the oxide being hidden from the polymer.

Some polyester and polycarbonate-based waterborne polyurethanes (WPU) were characterised by means of several techniques, to correlate the morphology with their structures and properties. The morphological analysis carried out by transmission electron microscopy on thin sections showed that the selected polyurethanes, after purification, exhibit a nanostructured phase separation between hard and soft domains. The presence of hydrogen bonding and the hard/soft ratio were evaluated by FT IR and NMR spectroscopy. Both the thermal and the dynamic mechanical analysis allowed the polymers microstructure to be correlated with the polymer properties; two glass transition temperatures were determined, corresponding to the hard and soft domains respectively.

In this article, the Lattice Cluster Theory developed by Freed and coworkers is applied to the poly(styrene)/poly(vinyl methylether) system by measuring the enthalpy and the volume variation associated with the mixing of the two homopolymers. It comes out that the chains architectures previously chosen for the two macromolecules based on the phase diagram and of the partition function developed by the theory correctly predicts the sign of both ΔHM and ΔVM. The foreseen trends as function of mixture composition fit the experimental data only for ΔVM; ΔHM is higher than predicted, asymmetrical and independent on the chain lengths of the components. The conclusion is that the theory needs some final touches in order to obtain a better agreement with experiments. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 791–797, 2008

In the preservation of Cultural Heritage items, the use of polymeric materials for the consolidation and protection of artifacts with historical and artistic value is widely accepted, except for cellulose-based materials, since here there are no suitable products and appropriate application techniques. Grafting polymerization of acrylic monomers onto cellulose chains represents an innovative method of restoration for both artificially and naturally aged textiles. In this article, some results concerning the grafting polymerization of ethyl acrylate/ethyl methacrylate 75/25 and ethyl acrylate/methyl methacrylate/trifluoroethyl methacrylate 73/24.5/2.5 polymers onto linen and cotton are reported. The effectiveness of grafting polymerization as a method for textiles conservation is discussed. The consolidating and protective effects were investigated by evaluating the mechanical properties and the wetting behavior of the grafted samples, and comparing them with the original and aged substrates. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 90–99, 2007

An oxidative reaction of cellulose with sodium methaperiodate was performed in order to reproduce the natural ageing of textiles. The oxidised groups were transformed into free macroradicals by treatment with UV light. In presence of acrylic monomers in the vapour phase, these reactive sites become the starting point for the graft copolymerisation of methyl methacrylate and ethyl acrylate onto cellulose. Thermal analysis is a convenient, useful and reproducible method for characterising complex organic materials from plants. In this research we have examined the thermal stability of oxidised and grafted flax and cotton using differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) analyses, in order to evaluate the effect of the grafting on their thermal behaviour. In presence of acrylic grafted polymer, the thermal stability of the textiles increases.

Polymeric products are largely used for consolidation of stone in the field of cultural heritage. Nevertheless, the main problem of polymeric compounds is related to their macromolecular nature, it being difficult for a polymer to penetrate inside the pores which may have a very small diameter. These considerations are the starting points for in situ polymerization. According to this technique, not the pre-formed polymer, but the monomer is introduced into the stone and it is polymerized in situ in a subsequent step. Frontal polymerization (FP) is a particular technique in which the heat released by the exothermal reaction of monomer to polymer conversion is exploited to promote the formation of a hot traveling front able to propagate and self-sustain the reaction. In the present work, FP is performed inside the pores of the stone and the results lead to the conclusion that the hot front is still active in the presence of an inorganic material which dissipates partially the heat released during the polymerization. In addition some recent applications of FP are discussed in comparison with the traditional polymerization for the in situ consolidation and protection of stones. Copyright © 2005 John Wiley & Sons, Ltd.

Estimate of sorption of liquid materials inside porous stones is an important parameter in industrial material testing and cultural heritage conservation. In the latter case, a suitable polymer can be used for both consolidation and conservation, it being applied either in the final form or as its parent monomer, which is subsequently allowed to polymerize in situ by the classical method or by frontal polymerization. However, the sorption of such materials through the stone is often difficult because of their viscosity and/or stone porosity. For this reason, the amount of monomer (or polymer) is a parameter of great interest in order to determine the extent of protection reachable by the treatment. In this paper a new methodology based on X-ray tomography is presented. The methodology makes use of a contrast agent added to the monomer that does not interact with its propagation inside the stone and allows to increase the absorption coefficient and so to observe the monomer inside the sample, which is finally frontally polymerized.

The effectiveness of butyl methacrylate/ethyl acrylate-based copolymers as consolidants for stone was investigated. The penetration of polymeric consolidating products is extremely slight because of their macromolecular nature and in situ polymerization of the monomers is suggested as an alternative technique to the use of macromolecular solutions. The efficiencies of three products synthesized in situ and fluorinated by various copolymers were comparatively evaluated in terms of surface properties, water permeability, and consolidation on a selected stone substrate. Moreover, because the environmental stability of such polymeric products is one of the key factors for their extensive application for conservative treatments, the photooxidative stability of reference polymers prepared in vitro was also investigated. © 2004 Wiley Periodicals, Inc.

An oxidative reaction of cellulose with sodium metaperiodate was performed. The oxidised groups were decomposed by treatment with UV light into free macroradicals. In the presence of acrylic monomers, in the vapour phase, these reactive sites become the starting points for the graft copolymerisation of the cellulose substrate. In this study we examined the graft yield as a function of the polymerisation time and the oxidation degree of cellulose. The grafted polymer was characterised using several analytical techniques, DSC analysis, GPC analysis, viscosity, FTIR and 13C CP-MAS. Information on the morphology of grafted chains with respect to the bulk cellulose was obtained, measuring the dynamic parameters in a careful 13C CP-MAS NMR study. All proposed chemical reactions, if properly conducted, do not affect the crystallinity of cellulose and introduce only a very modest amount of oligomers, therefore they seem suitable for the consolidation and protection of precious cellulose based materials, which are of historical interest.

The miscibility of chitosan and poly(vinyl pyrrolidone) -PVP- has been studied by viscosity measurements, differential scanning calorimetry (DSC) and Fourier transform infrared spectroscopy (FTIR). For chitosan/PVP blends in solid state (thin films) interaction were found by FTIR and DSC methods. After blending PVP with chitosan the glass transition temperature Tg was altered, this may be a result of hydrogen bonds between the synthetic and biological component. It was found that solution of chitosan and PVP are immiscible, viscosimetry methods showed that interactions between chitosan and PVP are to small for the predictions of miscibility, due to the high affinity of the two polymers for the solvent. The study of blends with bespoke structural and properties will be essential for the development of a new generation of biocompatible stimuli-sensitive hydrogels.

In this paper the consolidating and protective products used in the restoration of stone manufactured objects of artistic interest are discussed; advantages of the different products and the relevant properties of the polymeric materials are underlined. The penetration of polymeric consolidating materials is very small and the in situ polymerisation of the monomers is suggested as an alternative technique to using macromolecular solutions. Some experimental results are presented showing that the in situ polymerisation improves the consolidating and the protective properties of polymers.

Synthetic polymers have been occasionally applied to the consolidation and protection of paper and cellulose-based textiles especially when traditional conservation methods were not sufficient to improve the mechanical resistance of the degraded artefacts. In this paper, the potential of the innovative technique of grafting polymerisation with synthetic polymers was investigated to prevent biodeterioration. Cotton, linen and Whatman paper were consolidated by a) coating Paraloid B72®, b) coating ethyl acrylate/methyl methacrylate (EA/MMA) preformed copolymer, and c) grafting onto cellulose chains EA and MMA monomers in the ratio 75/25. All the samples were artificially biodeteriorated to obtain biodegraded model samples of both consolidated and non-consolidated substrates, according to the ASTM G21-96(2002) Standard Practice for Determining Resistance of Synthetic Polymeric Materials to Fungi. The consolidating effect was examined evaluating the mechanical behaviour of the grafted and coated samples, before and after the artificial biodeterioration. In addition, SEM observations were applied to monitor both the grafting level and.the biodeterioration of the samples. With the grafting of acrylic monomers, the mechanical strength of cellulose-based textiles and paper was greatly improved, as well as the resistance to biological agents. Therefore, with regards to biodeterioration, the graft copolymer EA/MMA (75/25 wt) was proved to be a suitable method to help prevent possible deterioration of paper and textiles.

Consolidation treatment of porous materials was performed by in situ and frontal polymerization of acrylic monomers inside a porous stone. To study the penetration of the polymer inside the stone and its consolidating effects we used water as a contrast agent, detecting its penetration using unilateral NMR and magnetic resonance imaging. All data obtained on differently treated stones were compared with corresponding ones obtained analyzing both untreated stones and stones simply painted with a well-known polymeric protective agent. In situ polymerization of acrylic monomers inside porous stones has been demonstrated to be an extremely powerful consolidating method, whereas thermally initiated frontal polymerization seems less efficient. In both cases the optimal choice of monomers is still open and requires further study. Our data indicate that unilateral NMR represents an inexpensive and simple technique for the non-invasive observation of the water uptake and of the effect of consolidation procedures in porous materials.

In the preservation of cultural heritage items, the use of polymeric materials for the consolidation and protection of artifacts with historical and artistic value is widely accepted. This area is vast and includes studies of various objects made of different materials such as wood, stone, textiles, and paper. The aim of this article is to establish the most suitable copolymer for cellulose-based-material restoration according to its properties, as evaluated by several techniques such as 1H-NMR spectroscopy, size exclusion chromatography, differential scanning calorimetry, and dynamic mechanical analysis. In addition to the mechanical property evaluation, an investigation of fungal deterioration has been carried out. Because, in the literature, no complete study concerning the characterization of ethyl acrylate/methyl methacrylate and butyl acrylate/methyl methacrylate copolymers is available, a detailed and full investigation of these polymers is required before the best copolymer is selected for grafting polymerization onto cellulose. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 1157–1164, 2005

Conversion of dihydroxyl groups to dialdehyde by periodate oxidation is a useful method widely used in derivatization of cellulose to activate the polymer to further reactions as grafting polymerization. To investigate the cellulose behavior at different level of oxidation and to better understand the influence of the crystallinity on the effects induced by oxidative reactions on different cellulose materials, linen and cotton textiles have been oxidized with periodate solutions in different conditions. Oxidized cellulose samples have been characterized by several techniques: solid-state 13 C NMR, Wide Angle X-Ray diffraction, and SEM. Moreover the mechanical properties of the untreated and oxidized yarns have been evaluated by means of tensile tests, the oxidation degree has been measured by means of the hydroxylamine hydrochloride method.

The miscibility of poly(styrene) and poly(vinylmethylether) is studied both by measuring the glass transition temperatures of the mixture and with the application of the Flory–Prigogine theory in the approximated form due to Patterson. For these calculations, the enthalpy of mixing of the two polymers is evaluated by measuring the enthalpies of solution of the pure polymers and of the mixture. The trend of the interaction parameters with the temperature for two samples of poly(styrene) of different molecular weight is discussed.

The specific volume and the coefficient of thermal expansion of poly(styrene), poly(vinyl methyl ether) and their mixtures and measurement: the thermal coefficient of the pressure was calculated using the group contributions. From these data the characteristic parameters v*, T*, p* of the Flory's state equation are determined. Considerations on the theretical previsions and experimental curves are also carried out.