Quantitative description of aggregation and dissociation of poly (vinyl methyl ether)/poly (2-ethyl-2-oxazoline) chains in water by novel elastic light scattering spectroscopy

Phase transition process in aqueous solutions of poly (vinyl methyl ether) (PVME)/poly (2-ethyl-2-oxazoline) (PEtOx) mixtures was investigated by elastic light scattering (ELS) spectroscopy. The two temperatures of phase transition in solutions during heating were identified, corresponding to different lower critical solution temperatures of PVME and PEtOx. The ELS spectra revealed the aggregation of molecular chains in the course of phase transition. It was found that PVME chains collapsed and aggregated during heating. Afterward, the PEtOx chains began to aggregate. In contrast, during cooling, the PEtOx aggregates were initially swelled and followed by partial dissociation. This was probably because that the PVME aggregates formed in solution might sterically hinder the further swelling and dissociation of the PEtOx aggregates. Subsequently, the aggregates of PVME chains and the independent PEtOx aggregates swelled and dissociated, while the conformation of molecular chains finally returned to its original state. In view of the phase transition behavior of PVME/PEtOx solutions, the mixtures of two thermosensitive polymers might be used to develop new polymeric materials possibly applied in fields such as drug delivery, biosensor, and bioseparation. Moreover, a model was proposed to describe the phase transition process.     

Pressure-volume-temperature properties for binary and ternary polymer solutions of poly(ethylene glycol), poly(propylene glycol), and poly(ethylene glycol methyl ether) with anisole

Pressure-volume-temperature properties were measured for polymer solutions of poly(propylene glycol) (PPG)+anisole, polymer blends of PPG+poly(ethylene glycol methyl ether) (PEGME), and the blends of PPG+PEGME and poly(ethylene glycol) (PEG)+PPG with anisole at temperatures from 298.15 to 348.15 K and pressures up to 50 MPa. The Tait equation represents accurately the pressure effect on the liquid densities over the entire pressure range. The excess volumes change from positive to negative as increasing the mole fraction of PPG in the binary systems of PPG+anisole and PPG+PEGME. The volumetric data of the related binary systems were correlated with the Flory-Orwoll-Vrij and the Schotte equations of state to determine the binary parameters. By using these determined binary parameters, both equations predicted the specific volumes of the polymer blends with anisole to average absolute deviations of better than 0.13%.     

Noble gas transport in poly(methyl vinyl ketone) and poly(methyl vinyl ether)

A systematic study and interpretation of the transport parameters characterizing the permeation of the noble gases, He, Ne, Ar and Kr through poly(methyl vinyl ketone) and poly(methyl vinyl ether) are presented. The results and correlations are compared with related measurements on poly(methyl acrylate) and poly(vinyl acetate). In general the measurements were conducted above the glass transition temperatures of the respective polymers. The results are interpreted in terms of the systematic variations in the physicochemical parameters of these closely related polymers. Free volume and dipoledipole interactions appear to dominate the observed behaviour and the composite results may be explained in these terms. The size distribution of the fluctuating free volume elements and chain stiffness are also to be considered.     

Characterization of poly(vinyl alcohol)/poly(ethylene glycol) hydrogels and PVA-derived hybrids by small-angle X-ray scattering and FTIR spectroscopy

The purpose of this study is to develop novel poly(vinyl alcohol) (PVA)/poly(ethylene glycol) (PEG) hydrogel blends and PVA-derived organic-inorganic hybrid materials and perform nanostructural characterizations. PVA and PEG hydrogels were prepared by dissolving the polymer in aqueous solution, followed by addition of glutaraldehyde (GA) chemical crosslinker. Hybrids were synthesized by reacting PVA in aqueous solution with tetraethoxysilane (TEOS). PVA/TEOS were also modified in the nanometer-scale by crosslinking with GA during the synthesis reaction. Hydrogels and hybrids were characterized by using small-angle X-ray scattering synchrotron radiation (SAXS) and Fourier transform infrared spectroscopy (FTIR). Thin film samples were prepared for SAXS experiments. SAXS results have indicated different nano-ordered disperse phases for hydrogels made of PVA, PEG, PVA/GA, PVA/PEG. Also, PVA/TEOS and PVA/TEOS/GA hybrids have indicated different X-ray scattering patterns. FTIR spectra have showed major vibration bands associated with organic-inorganic chemical groups present in the hybrid nanocomposites PVA/TEOS and PVA/TEOS/GA. PVA/PEG hydrogels and PVA-derived hybrid materials were successfully produced with GA crosslinking in nanometer-scale network.     

Development of stealth nanoparticles coated with poly(2-methoxyethyl vinyl ether) as an alternative to poly(ethylene glycol)

Poly(ethylene glycol) (PEG) modification, also known as PEGylation, has been extensively used to improve the stability of nanoparticles for nanomedical applications. However, PEG exhibits antigenicity in some formulations, motivating researchers to explore alternative polymers. Herein, poly(vinyl ether) (PVE) derivatives are highlighted as promising alternatives to PEG because they form intermediate water molecules that suppress non-specific protein adsorption and platelet adhesion to the material surface. We prepared a water-soluble PVE derivative, poly(2-methoxyethyl vinyl ether) (PMOVE), and utilized it as a surface modifier for gold nanoparticles (AuNPs) as model nanoparticles. PMOVE with a thiol terminus was synthesized and confirmed to form an intermediate water molecule using differential scanning calorimetry. Similar to the synthesis of PEGylated AuNPs (PEG-AuNPs), PMOVE-modified AuNPs (PMOVE-AuNPs) were successfully fabricated with an appreciably high density of PMOVE palisades via a thiol-gold coordination reaction. Similar to PEG-AuNPs, PMOVE-AuNPs showed reduced serum protein adsorption and prolonged blood circulation. Additionally, no significant cytotoxicity was observed after incubation of a murine macrophage cell line, RAW264.7, with PMOVE-AuNPs. Our results indicate that the PMOVE modification increases the stealthiness of nanoparticles that is equivalent to that achieved by PEGylation.     

Imparting antifouling properties of silicone hydrogels by grafting poly(ethylene glycol) methyl ether acrylate initiated by UV light

Both hydrophilic and antifouling surfaces were prepared on silicone hydrogels with poly(ethylene glycol) methyl ether acrylate (PEGMA) grafted by UV-induced radical polymerization. The PEGMA-grafted silicone hydrogels were characterized by graft yield and static water contact angle measurements. According to the results, the graft yield reached a maximum at 8 min of UV exposure time and 20 wt% PEGMA concentration. The modified silicone hydrogels possessed hydrophilic surfaces with the lowest water contact angle of 36°. The oxygen permeability and transparency of the PEGMA-grafted silicone hydrogels were as high as the unmodified silicone hydrogel. The mechanical property of silicone hydrogels was maintained at about 95% of the tensile strength and elastic modulus after the PEGMA grafting. The in vitro single protein adsorption on the PEGMA-grafted silicone hydrogels decreased by 70–80% compared to the unmodified silicone hydrogel. The PEGMA-grafted silicone hydrogel is expected to be a novel biomaterial, which possesses excellent surface hydrophilicity, antifouling property, oxygen permeability, and mechanical property. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Deformation studies of polystyrene/poly(vinyl methyl ether) blends by mechanical-vibrational spectroscopy

We have analyzed the deformation behavior of compatible and incompatible polystyrene (PS) and poly(vinyl methyl ether) (PVME) blends by a combination of mechanical and vibrational spectroscopy. Macroscopic properties and segmental orientation were found to be sensitive to molecular weight, strain rate, and temperature of measurement above the glass-transition temperature. Considerably different orientation functions were found for the PS and PVME components. For the experiments carried out above the T_g of the blends, the deformation behavior measured was consistent with expectations of a rubbery network.     

Biodegradability of poly(ethylene terephthalate) copolymers with poly(ethylene glycol)s and poly(tetramethylene glycol)

Poly(ethylene terephthalate) copolymers were prepared by melt polycondensation of dimethyl terephthalate and excess ethylene glycol with 10–40mol% (in feed) of poly(ethylene glycol) (E) and poly(tetramethylene glycol) (B), with molecular weight (MW) of E and B 200–7500 and 1000, respectively. The reduced specific viscosity of copolymers increased with increasing MW and content of polyglycol comonomer. The temperature of melting (T_m), cold crystallization and glass transition (T_g) decreased with the copolymerization. T_m depression of copolymers suggested that the E series copolymers are the block type at higher content of the comonomer. T_g was decreased below room temperature by the copolymerization, which affected the crystallinity and the density of copolymer films. Water absorption increased with increasing content of comonomer, and the increase was much higher for E1000 series films than B1000 series films. The biodegradability was estimated by weight loss of copolymer films in buffer solution with and without a lipase at 37°C. The weight loss was enhanced a little by the presence of a lipase, and increased abruptly at higher comonomer content, which was correlated to the water absorption and the concentration of ester linkages between PET and PEG segments. The weight loss of B series films was much lower than that of E series films. The abrupt increase of the weight loss by alkaline hydrolysis is almost consistent with that by biodegradation.     

Physicochemical characterization of poly(ethylene glycol) plasticized poly(methyl vinyl ether‐co‐maleic acid) films

The influence of the poly(ethylene glycol) (PEG) plasticizer content and molecular weight on the physicochemical properties of films cast from aqueous blends of poly(methyl vinyl ether‐co‐maleic acid) (PMVE/MA) was investigated with tensile mechanical testing, thermal analysis, and attenuated total reflectance/Fourier transform infrared spectroscopy. Unplasticized films and those containing high copolymer contents were very difficult to handle and proved difficult to test. PEG with a molecular weight of 200 Da was the most efficient plasticizer. However, films cast from aqueous blends containing 10% (w/w) PMVE/MA and either PEG 1000 or PEG 10,000 when the copolymer/plasticizer ratio was 4 : 3 and those cast from aqueous blends containing 15% (w/w) PMVE/MA and either PEG 1000 or PEG 10,000 when the copolymer/plasticizer ratio was 2 : 1 possessed mechanical properties most closely mimicking those of a formulation we have used clinically in photodynamic therapy. Importantly, we found previously that films cast from aqueous blends containing 10% (w/w) PMVE/MA performed rather poorly in the clinical setting, where uptake of moisture from patients' skin led to reversion of the formulation to a thick gel. Consequently, we are now investigating films cast from aqueous blends containing 15% (w/w) PMVE/MA and either PEG 1000 or PEG 10,000, where the copolymer/plasticizer ratio is 2 : 1, as possible Food and Drug Administration approved replacements for our current formulation, which must currently be used only on a named patient basis as its plasticizer, tripropylene glycol methyl ether, is not currently available in pharmaceutical grade. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Synthesis of monomethoxy poly(ethylene glycol) without diol poly(ethylene glycol)

Since monomethoxy poly(ethylene glycol) (mPEG) inevitably contains diol PEG and is difficult to get high molecular weight through traditional synthesis at high temperature under high pressure, a novel synthetic technique via anionic solution polymerization was reported in this study. With a new initiating system, potassium naphthalene and methanol, was introduced, the polymerization proceeded at ambient temperature and side reactions were well restrained. Furthermore, a slight excess of potassium naphthalene can effectively remove the trace of water and oxygen in the reaction system. Under this condition, mPEG was nearly quantitatively obtained without containing diol PEG. Its Mn ranged from 1 to 30 kDa and the polydispersity was kept lower than 1.07. Characterization of the mPEG obtained was carried out using GPC to determine the content of diol PEG and ¹H‐NMR and MALDI‐ToF MS spectroscopic analysis to confirm the exact structure. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007     

Incoherent neutron scattering study on the local dynamics in polystyrene and poly(vinyl methyl ether) blends

Neutron scattering study using the fixed elastic window technique is performed to investigate the effect of blending on the local dynamics of each component for polystyrene and poly(vinyl methyl ether) blends. The non-Gaussian scattering behavior observed above a certain temperature for the PVME component can be well explained by considering the rotational motions of methyl groups around O-CH₃ axis. The mean-square displacements of the vibrational motions were approximately proportional to absolute temperature below the glass transition temperature, which is a signature of harmonic oscillations, and were hardly affected by blending PS. On the other hand, the mean-square displacement of the PS component in the blend was almost the same as that of pure PS, while the non-Gaussian parameter for the former was much larger in comparison with that of the latter. Blending with PVME leads to a large increase in the dynamical heterogeneity for the PS component.     

Comparison of interdiffusion at polystyrene–poly(vinyl methyl ether) and polystyrene–poly(isobutyl vinyl ether) interfaces

The effect of polymer–polymer compatibility on interdiffusion at polymer interfaces with dissimilar mobilities was investigated by attenuated total internal reflectance infrared spectroscopy. The polymer pair consisting of polystyrene and poly(vinyl methyl ether) was used to study interdiffusion at the interface of compatible polymers. The polymer pair consisting of polystyrene and poly(isobutyl vinyl ether) was used to study interdiffusion at the interface of incompatible polymers. Results indicate that the extent of interdiffusion is controlled by the polymer–polymer compatibility parameter, irrespectively of the differences in the mobility of the polymers.     

Frozen bound water melting induced cooperative hydration of poly(vinyl methyl ether) in aqueous solution

Summary Poly(vinyl methyl ether) aqueous solution (30 wt.-%) at low temperature has been investigated by DSC and FTIR spectroscopy. Below −20°C, there are two types of ice formed by free water and frozen bound water respectively. When the ice formed by frozen bound water melts, the PVME begins to form hydrogen with water. A cooperative hydration phenomenon is observed in this system between −20 ∼−6°C during heating. FTIR data also show that hydrogen bonds between water molecules and polymer groups are broken completely before the cooperative hydration happens. This indicates that the unfrozen bound might not exist in 30 wt.-% PVME aqueous solution at low temperature. Received: 27 December 2001/Revised version: 4 March 2002/ Accepted: 5 March 2002     

Block copolymerization of poly(ethylene glycol) with methyl methacrylate using redox macroinitiators

A series of block copolymers of poly(ethylene glycol) (PEG) with methyl methacrylate (MMA) were prepared using a redox system consisting of ceric ion and PEG of various molecular weights in aqueous medium. The block copolymerization experiments were carried out under such conditions in which there was no homopolymerization of MMA by Ce⁴⁺ alone. The intermediacy of the PEG macroradical in the redox process was substantiated by ESR spectroscopy and a polymerization proceeding through ‘blocking from’ mechanism was postulated. The formation of the block copolymers was confirmed by chemical test and fractional precipitation as well as by FT-IR and FT-NMR (¹H and ¹³C-(¹H)) spectroscopy. The triblock nature of the block copolymers was ascertained through the cleavage of the ether linkage of the PEG segment. Simultaneous TG/DTA studies of the block copolymers revealed multiple stage decomposition patterns and their DSC curves exhibited two glass transition temperatures. GPC investigation of the block copolymers revealed unimodal molecular weight distribution with M_n values showing a smooth increase with ascending molecular weights of PEG. SEM studies indicated a fine dispersion of PEG in the continuous PMMA matrix.     

Self-assembly of thermo-responsive poly(oligo(ethylene glycol) methyl ether methacrylate)-C60 in water-methanol mixtures

Well-defined statistical copolymer of poly (di(ethylene glycol) methyl ether methacrylate-stat-oligo(ethylene glycol) methyl ether methacrylate-C₆₀ ((PMEO₂MA-stat-POEGMA₃₀₀)-C₆₀) was synthesized via atom transfer radical polymerization (ATRP) reaction and atom transfer radical addition (ATRA) processes. The lower critical solution temperature (LCST) of PMEO₂MA-stat-POEGMA₃₀₀ increased from 42 to 95 °C when the amounts of methanol was increased from 0 to 30 vol%, beyond which the LCST could not be quantified. Similarly, the LCST of (PMEO₂MA-stat-POEGMA₃₀₀)-C₆₀ also increased with methanol content, however it was lower than PMEO₂MA-stat-POEGMA₃₀₀ for all methanol/water compositions. The CMC of (PMEO₂MA-stat-POEGMA₃₀₀)-C₆₀ increased with increasing methanol content, suggesting that methanol is a better solvent for PMEO₂MA-stat-POEGMA₃₀₀ segment. The amphiphilic (PMEO₂MA-stat-POEGMA₃₀₀)-C₆₀ structure formed spherical micelles in water/methanol mixture, and larger micelles were formed at higher methanol content. The hydrodynamic radius (R_h) remained constant at temperature below the LCST. It increased dramatically at temperature greater than the LCST, and the (R_g/R_h) increased from ∼0.75 to ∼1.0. We believe that the (PMEO₂MA-stat-POEGMA₃₀₀) coronas dehydrate at higher temperature, and the micelles associate to form larger aggregates. In water/methanol mixtures, core-shell micelles and large compound micelles are produced below and above the LCST respectively.     

Filled temperature‐sensitive poly(vinyl methyl ether) hydrogels

Temperature‐sensitive hydrogels based on poly(vinyl methyl ether) (PVME) with ferroelectric or ferromagnetic properties were synthesized by high‐energy irradiation. Barium titanate and poly(vinylidene fluoride) (PVDF) were used as ferroelectric filler and Ni as ferromagnetic filler. The filled PVME hydrogels were synthesized by electron beam or γ‐ray irradiation (of a suspension with 5–50 wt % of filler (with respect to polymer mass) in a 20 wt % aqueous PVME solution). Filling of the gel reduces the absolute swelling degree at low temperatures, but do not influence the phase‐transition temperature of the gel. The particle distribution of the fillers inside the gel was visualized by field emission scanning electron microscopy. The fillers were incorporated in the PVME network and fixed because of their size (inorganic particles), as well as by chemical bonds (PVDF). The ferroelectric or ferromagnetic properties of the filled gels were proved. Measurements in a corresponding alternating field provide the hysteresis loop, for both the ferromagnetic and ferroelectric gel. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 2253–2265, 2005     

Molecular relaxation in cross-linked poly(ethylene glycol) and poly(propylene glycol) diacrylate networks by dielectric spectroscopy

The molecular relaxation characteristics of rubbery amorphous crosslinked networks based on poly(ethylene glycol) diacrylate [PEGDA] and poly(propylene glycol) diacrylate [PPGDA] have been investigated using broadband dielectric spectroscopy. Dielectric spectra measured across the sub-glass transition region indicate the emergence of an intermediate “fast” relaxation in the highly crosslinked networks that appears to correspond to a subset of segmental motions that are more local and less cooperative as compared to those associated with the glass transition. This process, which is similar to a distinct sub-T_g relaxation detected in poly(ethylene oxide) [PEO], may be a general feature in systems with a sufficient level of chemical or physical constraint, as it is observed in the crosslinked networks, crystalline PEO, and PEO-based nanocomposites.     

Miscibility of polystyrene with poly(ethylene oxide) and poly(ethylene glycol)

The intrinsic viscosity of polystyrene–poly(ethylene oxide) (PS–PEO) and PS–poly(ethylene glycol) (PEG) blends have been measured in benzene as a function of blend composition for various molecular weights of PEO and PEG at 303.15 K. The compatibility of polymer pairs in solution were determined on the basis of the interaction parameter term, Δb, and the difference between the experimental and theoretical weight-average intrinsic viscosities of the two polymers, Δ[η]. The theoretical weight-average intrinsic viscosities were calculated by interpolation of the individual intrinsic viscosities of the blend components. The compatibility data based on [η] determined by a single specific viscosity measurement, as a quick method for the determination of the intrinsic viscosity, were compared with that obtained from [η] determined via the Huggins equation. The effect of molecular weights of the blend components and the polymer structure on the extent of compatibility was studied. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 69: 1471–1482, 1998     

Rheological studies of disulfonated poly(arylene ether sulfone) plasticized with poly(ethylene glycol) for membrane formation

Disulfonated poly(arylene ether sulfone) (BPS) random copolymers, prepared from a sulfonated monomer, have been considered for use as membrane materials for various applications in water purification and power generation. These membranes can be melt-processed to avoid the use of hazardous solvent-based processes with the aid of a plasticizer, a low molecular weight poly(ethylene glycol) (PEG). PEG was used to modify the glass transition temperature and melt rheology of BPS to enable coextrusion with polypropylene (PP). Our previous paper discussed the miscibility of BPS with PEG and the influence of PEG on the glass transition of BPS. In this study, the rheological properties of disulfonated poly(arylene ether sulfone)s plasticized with poly(ethylene glycol) (PEG) are investigated to identify coextrusion processing conditions with candidate PPs. The effects of various factors including PEG molecular weight, PEG concentration, temperature and BPS molecular weight on blend viscosity were studied. The rheological data effectively lie on the same master curve developed by Bueche and Harding for non-associating polymers such as poly(methyl methacrylate) (PMMA) and polystyrene (PS). Although sulfonated polysulfone contains ionic groups, the form of its viscosity versus shear rate (or frequency) behavior appears to be dominated by the relaxation of polymer entanglements.