Amphiphilic enzyme membranes,I. Preparation of amphiphilic membranes using poly(HEMA) and poly(HEMA-co-st)

Copolymers of 2-hydroxyethyl methacrylate (HEMA) and styrene (St) with various HEMA contents were synthesized in this investigation. Amphiphilic membranes were fabricated by using one layer of hydrophilic poly(HEMA) and one layer of hydrophobic poly(HEMA-co-St) in the presence of a photosensitizer. The oxygen permeability and the water penetration of the amphiphilic membranes with various HEMA contents were estimated. The dependence of the mole fraction of HEMA on hydrophilicity and binding forces on the surface of the amphiphilic membranes were investigated. Characteristics of the amphiphilic membranes on the enzyme immobilization were compared with those of traditional two-layer systems. The response time, stability and pH dependences of the amphiphilic enzyme membrane were also evaluated.     

The equilibrium water content of some thermoplastic hydroxyalkyl methacrylate polymers

The equilibrium water content (EWC) of thermoplastic 2-hydroxypropyl methacrylate and 2-hydroxyethyl methacrylate homopolymers from technical grade monomer and of copolymers of the latter with methyl methacrylate has been measured in distilled water and in phosphate-buffered saline (PBS). In distilled water, as expected, EWCs increased monotonically with the proportion of hydrophilic monomer in the polymer and showed only a small dependence on molecular weight. In contrast, the degree of swelling (and in some cases dissolution) and “freezable” water content of polymers in PBS were shown to be anomalously high and to be a consequence of ionization at pH 7.4 of methacrylic acid incorporated into the polymer in small quantity (< 1 mol %) as an impurity. Initial studies indicated a strong relationship between copolymer molecular weight and small molecule permeability in distilled water.     

Electron microscopy investigation of ion exchange membranes

Transmission electron microscopy has been used for the recognition of the structural heterogeneity and the distribution of ionogenic groups in the cation exchange membranes. The investigations were performed on the fluorinated membranes (NAFION, MRF) and on the earlier known membranes containing poly(styrenesulphonic acid) (AMF C-322 and PE—PSSA membranes). The electron images of the ultra-thin sections revealed the homogeneous nature with the uniform distribution of small ionogenic group concentrations in the membranes NAFION and MRF—4MB, and the heterogeneous distribution of the groups in the poly(styrenesulphonic acid) membranes (AMF C-322, PE—PSSA membrane) and the membrane MRF-26, which is the consequence of the inhomogeneous nature of the polymer base of these membranes.     

pH and temperature responsive porous membranes via an in situ bulk copolymerization approach

In the present study, an in situ approach to pH and temperature responsive membranes is developed. The membrane matrix is formed through bulk polymerization and crosslinking of liquid monomer 2-hydroxyethyl methacrylate (HEMA) while the membrane pores are formed by the templating of inorganic particles. The functional monomers methacrylic acid (MAA) and N-isopropylacrylamide (NIPAAm) are incorporated into membrane casting solution in order to confer membranes with pH and temperature responsive properties. The poly(HEMA/MAA) membranes exhibit a reversible pH-dependent water flux, while the poly(HEMA/NIPAAm) membranes exhibit a reversible temperature-dependent water flux. The flux of the poly(HEMA/MAA) membrane increased by 70% when pH was decreased from 10.0 to 2.0, while the flux poly(HEMA/NIPAAm) membrane increased by 150% when temperature was increased from 20 to 45 °C. The protein adsorption and antifouling performance of the poly(HEMA/MAA) and poly(HEMA/NIPAAm) membranes also exhibit pH and temperature responsive properties.     

The formation of interpolymer complexes and hydrophilic associates of poly(acrylic acid) and non‐ionic copolymers based on 2‐hydroxyethylacrylate in aqueous solutions

It is shown that the reaction between poly(acrylic acid) and a non‐ionic polymer may give two different products. One of them is the well‐known interpolymer complex stabilized by hydrogen bonds, and the other belongs to a relatively new class of compounds named hydrophilic interpolymer associates. Networks occurring in the dynamic mode of formation and destruction of hydrogen bond linkages represent the structure of the hydrophilic associates; a single molecule of polyacid may be linked with two or more molecules of non‐ionic polymer in such associates. The result of the reaction under consideration strongly depends on the ratio of volumes of swollen coils of ionogenic and electrically neutral macromolecules. Classical interpolymer complexes cannot be formed at a high degree of swelling of polyacid coils, which takes place at high pH values. In contrast, hydrophilic associates are formed under such conditions. © 2013 Society of Chemical Industry     

Temperature/pH dual responsive OPGMA based copolymeric hydrogels prepared by gamma radiation: an optimisation study

The purpose of this study was to attain oligo(propylene glycol) methacrylate (OPGMA) based hydrogels for different biomedical applications. Since the volume phase transition temperature (VPTT) of poly(oligo(propylene glycol) methacrylate) (POPGMA) homopolymer was below room temperature, it was necessary to tune the thermoresponsiveness and the VPTT to higher temperatures; radical copolymerisation of OPGMA with more hydrophilic and/or pH responsive monomers was used to adjust these values. A series of copolymeric hydrogels with different ratios of OPGMA, 2-hydroxyethyl methacrylate (HEMA) and itaconic acid (IA) was synthesised by gamma radiation. The swelling properties were preliminarily investigated over a wide pH (2.2–9.0) and temperature (4–80 °C) ranges. Additional characterization of their structure and properties was conducted by Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM) and differential scanning calorimetry (DSC). The presented results revealed temperature/pH dual responsive P(OPGMA/IA) and P(OPGMA/HEMA/IA) copolymers with large diversity in swelling properties, as a result of the addition of OPGMA thermoresponsive units with a lower critical solution temperature (LCST) and IA pH responsive units. It was demonstrated that VPTT can be significantly shifted to higher (e.g. body) temperatures at higher pH values (pH ≥ 4) by increasing the IA content in the hydrogel composition. Due to the possibility of making dual responsive copolymers in the manner explained in this paper, OPGMA based hydrogels show potential for different biomedical applications.     

Influence of copolymer composition on non-fickian water transport through glassy copolymers

The dynamic swelling behavior of poly(2-hydroxyethyl methacrylate-co-methyl methacrylate) and poly(2-hydroxyethyl methacrylate-co-N-vinyl-2-pyrrolidone) in water was followed at 37°C. The results were analyzed in terms of a simple non-Fickian transport equation, which expresses the fractional penetrant uptake as an exponential function of the diffusion time. The exponent n, which indicates Fickian or non-Fickian transport mechanism, was correlated to the content of the more hydrophilic component of the copolymer. Photomicrographs obtained with polarized light offer new information about the position and movement of the penetrant front in glassy, hydrophilic polymers.     

Interchain EDA complexes of poly[N-(2-hydroxyethyl) carbazolyl methacrylate] with poly (ω-hydroxyalkyl-3,5-dinitrobenzoyl methacrylate)s

Summary The solid state behavior of the interchain electron donor-acceptor (EDA) complexes of poly[N-(2-hydroxyethyl)carbazolyl methacrylate] (PHECM) with poly(ω-hydroxyalkyl-3,5-dinitrobenzoyl methacrylate)s (PDNBM-n) (where n is the number of methylene groups in the hydroxyalkyl group) with n=2, 3, 4, 5 and 6 was studied by differential scanning calorimetry. All these systems form thermodynamically miscible blends. The dependence of the glass transition temperature (T_g) on the blend composition can be best aproximated by the Kwei's equation.     

Novel polyurethane hydrogels for biomedical applications

Polyurethane hydrogels derived from UV-curable urethane prepolymer and hydrophilic monomers were prepared and their properties were evaluated. The urethane prepolymer used in this study contained well-defined hard segments centered with a polyether-based soft segment and end-capped with methacrylate groups. The hydrophilic monomers studied were 2-hydroxyethyl methacrylate (HEMA), N-vinyl pyrrolidone, and glycerol methacrylate. Methacryloxypropyl tris (trimethysiloxy) silane (TRIS) was also used in some cases to modify properties. All composition were UV-cured and formed hydrogels after hydration. The oxygen permeabilities of the hydrogels decreased as the water contents increased and increased as the TRIS content was increased. The tear strengths and moduli decreased as the water contents of the hydrogels increased. Most compositions studied have higher oxygen permeability and tear strength than poly(HEMA) because of the presence of urethane prepolymer in the composition.     

Synthesis of a poly(methyl methacrylate)‐b‐poly[2‐(N,N‐dimethylamino) ethyl methacrylate] block copolymer and its effects on the surface charges and pH‐responsive properties of poly(vinylidene fluoride) blend membranes

A poly(methyl methacrylate) (PMMA)‐b‐poly[2‐(N,N‐dimethylamino) ethyl methacrylate] (PDMAEMA) block copolymer was successfully synthesized by a reversible addition–fragmentation chain‐transfer method. The resulting copolymer was used to prepare poly(vinylidene fluoride) blend membranes via a phase‐inversion technique. The polymorphism, structure, and properties of the blend membranes were investigated by Fourier transform infrared spectrometry, scanning electron microscopy (SEM), ζ potential analysis, and filtration. The results indicate that PMMA‐b‐PDMAEMA could migrate onto the surface of the membrane during the coagulation process, and more of the β‐crystal phase appeared with the increase of the block copolymer in the membranes. The surface morphology and cross section of the membranes were also affected by the copolymer, as shown by SEM. The ζ‐potential results show that the surface charges of the membrane could be changed from positive to negative at an isoelectric point as the pH increased. The blend membrane also exhibited good pH sensitivity, and its water flux showed a great dependence on pH. The filtration experiment also indicated that the blend membrane had good hydrophilicity and antifouling properties. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40685.     

Poly(ethoxytriethyleneglycol acrylate) cryogels as novel sustained drug release systems for oral application

Novel temperature sensitive cryogels of poly(ethoxytriethyleneglycol acrylate) (PETEGA), with in situ entrapped active substance, are synthesized employing the UV irradiation technique and tested as matrix for controlled release of the hydrophilic drug verapamil hydrochloride. PETEGA cryogels are non-toxic materials and, due to the macroporous structure, exhibit a reversible, ultra-rapid volume phase transition at temperature ca. 31 °C. Carriers based on PETEGA cryogels possess sustained release of verapamil hydrochloride over a period of more than 8 h, which is attributed to the hydrophobic state of the polymer network at physiological temperature and the method of drug immobilization. Drug release characteristics of PETEGA cryogels are compared with another cryogel systems, based on polyacrylamide (PAAm), poly(N-isopropylacrylamide) (PNIPAAm) and poly(2-hydroxyethyl methacrylate) (PHEMA), obtained via the same method.     

Synthesis of amphiphilic network copolymers based on poly(ester dimethacrylates)

Poly(ester dimethacrylate) has been synthesized by condensation of the ɛ-caprolactone-based macromonomer and 2-hydroxyethyl methacrylate with dicyclohexylmethane diisocyanate. Network copolymers of different compositions capable of swelling in water, THF, and toluene are obtained by the free-radical copolymerization of poly(ester dimethacrylate) with N-isopropylacrylamide or 2-hydroxyethyl methacrylate. The rate constants and equilibrium swelling indices of network copolymers in these solvents are measured. The amphiphilic properties of the network copolymers can vary in a wide range depending on the composition of copolymers and the nature of a hydrophilic monomer. The copolymers of poly(ester dimethacrylate) with N-isopropylacrylamide are characterized by pronounced thermal sensitivity.     

Multiarm star polyglycerol-block-poly(HEMA) as a versatile precursor for the preparation of micellar nanocapsules with different properties

Well-defined multiarm star polymer with hyperbranched polyglycerol as core and poly(2-hydroxyethyl methacrylate) (PHEMA) as arms were used as precursor for the preparation of inverted and aqueous micellar nanocapsules. The partial modification of the hydroxyl groups of PHEMA arms with aliphatic chains led to the formation of inverted micellar nanocapsules. The hydrophilic dye encapsulation capacity of the inverted micelles can be enhanced significantly by transforming the inner hydroxyl groups of PHEMA arms into quaternized amine groups. The modification of the outer and inner hydroxyl groups of PHEMA arms with polyethylene glycol acid chloride and pivaloyl chloride, respectively, resulted in aqueous micellar nanocapsule.     

Reactive polymers, 51. The temperature behaviour of macroporous methacrylate sorbents

The behaviour of macroporous methacrylate copolymers was investigated in the temperature range between 20 and 270°C. On the basis of retention of methyl alcohol and n-decane a discontinuity at 40°C was recorded in all cases, interpreted by the increasing mobility of chains of surface layers of the polymer globules. This temperature agrees with the reported T_g value of poly(glycidyl methacrylate) and is independent of further substitution of the polymer chain with ionogenic groups. At 210–250°C depolymerization takes place; in the case of methacrylic acid copolymers cyclic anhydrides are formed, while in the case of esters alkyls are eliminated. Modified copolymers of 2,3-dihydroxypropyl methacrylate with ionogenic groups are more stable thermally — the depolymerization proceeds under the same conditions to a smaller degree. Heating is connected with changes in the morphology of particles and pores, and also in the polarity of the polymers noticeable by the ratio of retentions of alcohols and paraffins and by the heat of dissolution.     

Effect of the crosslinking agent on porous networks formation of hema-based copolymers

New copolymers of ethylene glycol dimethacrylate/2-hydroxyethyl methacrylate [poly(EGDMA-co-HEMA)],2,2′,2″-nitrilotriethyl triacrylate/2-hydroxyethyl methacrylate [poly(NTETA-co-HEMA)] and pentaerythritol tetraacrylate/2-hydroxyethyl methacrylate [poly(PETA-co-HEMA)] were obtained by suspension polymerization at 70 or 85 °C, using cyclohexane (Cyc) as porogen. In this work, the influence of the crosslinking agent (di, tri, or tetravinyl monomer) on the morphology of the polymeric networks was investigated. Swelling studies, Fourier Transform Infrared (FTIR) and mercury intrusion porosimetry, demonstrated that when both the vinyl groups number and molecular chain length between double bonds of the crosslinking agent decreased, networks with high porosity and crosslinking degree were generated.     

Miscible blends of poly(styrene-co-acrylonitrile) and poly(α-methyl styrene-co-acrylonitrile) with hydroxyl-containing polymethacrylates

Poly(styrene-co-acrylonitrile)(SAN) and poly(α-methyl styrene-co-acrylonitrile)(MSAN) are miscible with poly(2-hydroxyethyl methacrylate) (PHEMA) and with poly(2-hydroxypropyl methacrylate) (PHPMA). That SAN and MSAN are immiscible with poly(n-propyl methacrylate) and with poly(isopropyl methacrylate) but miscible with PHPMA indicates the enhancement of polymer miscibility due to hydroxyl groups. The miscibility of these blends is explained in terms of recent theories for copolymer/homopolymer blends.     

Radiation-grafted hydrogels for biomaterial applications as studied by the ESCA technique

Electron spectroscopy for chemical analysis (ESCA) was used to study the surface composition of several radiation-grafted polymers in both the dry and hydrated (frozen at 160°K) states. Poly(2-hydroxyethyl methacrylate) (HEMA) and polyacrylamide, both hydrophilic polymers, were readily detected in the hydrated or dehydrated states when grafted to polyethylene substrates. For silicone rubber substrates, both grafts were observed on the hydrated surface but were significantly decreased in surface concentration upon dehydration. For grafts on a polyester-urethane, acrylamide was not a major constituent of either the dry or hydrated surface, while HEMA appeared to increase in abundance upon drying. The amount of the hydrophobic poly(ethyl methacrylate) found on the graft surface depended upon the substrate polymer used, but the surface abundance of poly(ethyl methacrylate) was not affected by drying. These results were considered in terms of polar group orientation, polymer chain mobility, substrate permeability, and the limitations of the ESCA technique. The implications of these results with respect to the use of radiation-grafted hydrophilic polymers for biomedical applications are also discussed.     

Well-defined poly(2-hydroxyethyl methacrylate) and its amphiphilic block copolymers via acidolysis of anionically synthesized poly(2-vinyloxyethyl methacrylate)

Summary A novel approach to a well-defined poly(2-hydroxyethyl methacrylate) [poly(HEMA)] and to its amphiphilic block copolymers was developed. The selective living anionic polymerization of the methacryloyl group of the bifunctional monomer 2-vinyloxyethyl methacrylate (VEMA) generated a functional polymer with a controlled molecular weight and a narrow molecular weight distribution (M_w/M_n= 1.05–1.09). This polymer is very stable under normal conditions. Being soluble in the common organic solvents, its characterization could be carried out easily. The unreacted vinyl groups in the side chains of the resulting polymer were further reacted with hydrochloric acid. This acidolysis changed poly(VEMA) to a well-defined poly(HEMA). In addition, the anionic block copolymerization of VEMA with styrene or methyl methacrylate also proceeded smoothly, generating the corresponding block copolymers. After acidolysis, these copolymers were turned into amphiphilic block copolymers containing a hydrophilic poly(HEMA) block. Received: 22 June 2001/Revised version: 15 August 2001/Accepted: 15 August 2001     

A water-soluble poly(methylphenylsilylene) derivative as a photoinitiator of radical polymerization of hydrophilic vinyl monomers

Summary Radicals formed during photoscission of the pyridinium salt of partially chloromethylated poly(methylphenysilylene) (Q-PMPSi) in aqueous solution are capable of initiating the polymerization of hydrophilic vinyl monomers, e.g. acrylic and methacrylic acid, acrylamide, 2-hydroxyethyl methacrylate and 1-vinyl-2-pyrrolidone.     

Charged ultrafiltration membrane for permeation of proteins

Polyacrylonitrile-g-poly(N,N-dimethylaminoethyl methacrylate) was synthesized photochemically and quaternized. The positively charged membranes made from the quaternized graftcopolymer showed high ultrafiltration rate for water by adding poly(vinyl alcohol) to casting solution and washing it out after the casting. In buffered saline solution, the permeability of the membranes was very small at pH below isoelectric point of albumin but increased markedly at higher pH. On the other hand, the permeability for γ-globulin was very small and did not show any pH dependence.