Copolymers Of 2-hydroxyethyl Methacrylate Research Articles

Network characteristics of homopolymer and some copolymers of poly(2‐hydroxyethyl methacrylate)

AbstractSoluble poly(2‐hydroxyethyl methacrylate) and copolymers of 2‐hydroxyethyl methacrylate with n‐butyl acrylate and 2‐hydroxypropyl acrylate of varying compositions were synthesised by solution polymerisation. The polymers were characterised by dilute solution viscometry and shear viscosity. Crosslinked membranes were prepared from these polymers by introducing crosslinks in solution state through the reaction with 1,6‐hexamethylene diisocyanate at a number of different crosslinker concentrations. The membranes swollen in dimethylformamide and water were characterised by performing equilibirium swelling measurements and calculating polymer volume fraction, the molecular mass between crosslinks (M̄c) and equilibrium water content (EWC) at 25°C. The calculation of M̄c used an expression developed by Peppas & Lucht for equilibrium swelling. This is a modified equation of the original Flory–Rehner expression, that allows non‐Gaussian distribution of chain lengths. The variation of M̄c with crosslinker concentration and copolymer composition is discussed in terms of structural and molecular characteristics of these highly crosslinked networks.

Characterization of surgical adhesives from UV‐polymerized poly(PEG dimethacrylate‐co‐2‐hydroxyethyl methacrylate) copolymers

AbstractPolymer samples that could be used as wound adhesives were prepared from poly(ethylene glycol)dimethacrylate (PEGDMA) and 2‐hydroxyethyl methacrylate (HEMA) copolymers in concentrations from 0 to 50 mol %. The UV copolymerization was initiated by 2,2‐dimethoxy‐2‐phenylacetophenone (DMPA) and ultraviolet light intensities ranged from 0.1 to 0.5 m W/cm. The volume shrinkage during photopolymerization was observed using a dilatometric technique. The overall volume shrinkage was affected by the comonomer ratio and the nature of the PEGDMA comonomer. The rate of volume shrinkage was higher at higher ultraviolet light intensities. PEG(400)DMA‐based copolymers exhibited lower glass transition temperatures than those of PEG(200)‐based copolymers. The introduction of HEMA to the copolymers reduced both their glass transition and degradation temperatures. The equilibrium water‐swelling ratio increased with increasing PEGDMA molecular weight and HEMA content. © 1995 John Wiley & Sons, Inc.

Effect of cationic groups on the adhesivity of peritoneal macrophages to polymeric beads

This study demonstrates the adhesion of macrophages to polymer beads from a copolymer of hydroxyethyl methacrylate and dimethyl aminoethyl methacrylate intraperitoneally injected into the rat. Dimethyl aminoethyl methacrylate exhibited a stimulatory effect on macrophage adhesion 5 h after injection of the beads. Electron microscopy demonstrated protein adsorption on the surface of the beads. Protein fibres between the cell surface and beads were observed. The experimental system used minimizes the influence of tissue damage at macrophage recognition of polymers. This method seems to be suitable for short-term investigation of macrophage-polymer interaction.

Solid-state dye lasers based on copolymers of 2-hydroxyethyl methacrylate and methyl methacrylate doped with rhodamine 6G

Rhodamine 6G has been dissolved in copolymers of 2-HydroxyEthyl MethAcrylate (HEMA) and Methyl MethAcrylate (MMA) and the resulting solid-state solutions have been pumped at 337 nm and 532 nm. Lasing efficiencies similar to those found in ethanol solution have been obtained with a 1:1 vol/vol HEMA: MMA copolymer matrix, and lifetimes of ca. 10 000 (337 nm pumping) and ca. 75 000 (532 nm pumping) pulses at repetition rates up to 15 Hz and 10 Hz, respectively, have been demonstrated.

Synthesis and rheological properties of soluble poly(hydroxyethyl methacrylate) and some copolymers

AbstractMethods to synthesise soluble poly(2‐hydroxyethyl methacrylate) (PHEMA) with varying molar mass were developed. Conversions over 90% were achieved without losing solubility. Steady state tests (range 0.01–590 Pa) and oscillatory tests (range 0.001–40 Hz) were carried out on 40% solutions in dimethyl formamide using a Carri‐Med rheometer. Only PHEMA having molar mass over 500000 showed significant shear thinning and viscoelastic properties. The copolymers of 2‐hydroxyethyl methacrylate (HEMA) with n‐butyl acrylate (BA) and 2‐hydroxypropyl acrylate (HPA) showed higher viscosities and viscoelastic properties compared with PHEMA homopolymer prepared under identical conditions. Also, viscosity and viscoelasticity increased with increase in acrylate content in the initial mixture. This was attributed to the higher molar mass of copolymers, which resulted from faster polymerisation rates owing to the inclusion of relatively highly reactive acrylates. However, in the case of HEMA : BA copolymers, first, the viscosity and viscoelasticity increased with increasing BA content and then dropped again, giving a maximum around HEMA : BA 75 : 25. This anomaly was explained by taking the effects of changes in inter‐and intra‐molecular hydrogen bonding as well as conformational differences caused by inclusion of BA in the PHEMA chain into account.

Effect of chloride on the release of chlorhexidine salts from methyl methacrylate: 2-hydroxyethyl methacrylate copolymer reservoir devices

Syntheses of copolymers of methyl methacrylate (MMA) and 2-hydroxyethyl methacrylate (HEMA) were carried out in solution without the addition of external covalent crosslinkers. Devices were formulated as coated matrices: 80% (w/w) chlorhexidine diacetate was incorporated in a core of 50:50 mole ratio HEMA:MMA copolymer and this matrix was then coated with 30:70 mole ratio HEMA:MMA copolymer. Coated devices released chlorhexidine into water for months with zero-order kinetics. In an inorganic saliva simulate, release rates were significantly lower than those observed from devices into water. Release rates were decreased 36% and 85% in 2.2 mM and 10 mM sodium chloride solutions, respectively. Hydration, pH, and osmotic effects were minimal. The effect of external chloride on the release rates was due to the conversion within the core of the acetate salt of chlorhexidine (solubility ~ 23 mg/ml at 37 °C) to the chloride salt (solubility ~ 1 mg/ml at 37 °C) and the consequent lower solubility. Addition of sodium chloride to a core formulation of chlorhexidine diacetate also resulted in lower release rates and presents as a facile method for release rate adjustment. For external chloride to diffuse into the core requires bulk water in the polymers for chloride transport. Differential scanning calorimetric studies indicated that each of the copolymers contained a significant amount of bulk water and hence a pathway for chloride transport from the external environment into the device core.

Synthesis and characterization of some photoresponsive polymers

Some photoresponsive polymers and copolymers of 2-hydroxyethyl methacrylate and ethyl methacrylate monomers were prepared by using 4-phenylazobenzoyl chloride as the chromophoric group. The polymers were characterized by elemental analysis method and by FTIR, NMR and mass spectroscopic techniques. Photoresponsive properties of the polymers were investigated by photoirradiation with u.v. light.

Laser action from a rhodamine 640-doped copolymer of 2-hydroxyethyl methacrylate and methyl methacrylate

Rhodamine 640 has been dissolved in a copolymer of 2-hydroxyethyl methacrylate (HEMA) and methyl methacrylate (MMA) 1:1 v/v and the resulting solid-state solution has been pumped with pulses of 1.7 mJ at 337 nm from a nitrogen laser. Laser action at 654 nm with energy conversion efficiency of ≈4% and lifetime of about 700 pulses at repetition rates up to 15 Hz has been demonstrated.

Changes of enantioselectivity with the substrate ratio for the addition of diethylzinc to aldehydes using a catalyst coupled to a soluble polymer

α,α-Diphenyl-L-prolinol, when coupled to a polymer soluble in organic solvents, gives surprising results for the addition of diethylzinc to aldehydes. For benzaldehyde, the enantiomeric excess strongly depends on the initial substrate ratio: an excess of diethylzinc yields (S)-1-phenylpropanol with up to 80% ee, while an excess of benzaldehyde leads to the (R)-1-phenylpropanol with up to 50% ee. The kinetic properties of the catalyst and the results with other aldehydes are also described. The polymer 1 is a copolymer of octadecyl methacrylate and 2-hydroxyethyl methacrylate.

Hydrolytically stable cellulose-derivative coatings for capillary electrophoresis of peptides, proteins and glycoconjugates.

A method for the preparation of versatile, hydrolytically stable coatings of fused silica capillaries is described. First, the HNO3-pretreated silica surface is reacted with 7-oct-1-enyltrimethoxysilane to form a stable self-assembled alkylsilane monolayer. Secondly, the copolymer of hydroxypropylcellulose and 2-hydroxyethyl methacrylate is statically coated onto a hydrophobized wall. This allows the formation of a highly crosslinked copolymer layer which is tightly bound to the wall surface. Hydrolytical stability in the pH range of 2-10 for several weeks has been demonstrated. The coating generates a low electroosmotic flow at alkaline pH, which can be easily masked by using special buffers. The versatility of this column technology is documented by separations of peptides, glycoproteins and derivatized oligosaccharides.

The thermal behaviour of water in hydrogels

The melting enthalpy and the absorption enthalpy of water in polymethacrylic acid and copolymers of methacrylic acid and hydroxyethylmethacrylate have been determined. The melting enthalpy of water in hydrogels increased by increasing the equilibration time at −15°C, but was always smaller than that of pure water. The absorption enthalpy of water was negative and decreased by increasing the initial water content of the hydrogels. However, the observed lack in melting enthalpy of water was not fully compensated by the negative change in absorption enthalpy. This led to the conclusion that a part of the water does not freeze during the cooling-heating process. The glass transition temperatures were determined as a function of the water content. Upon hydration, the glass transition temperature decreased in temperature. The amount of water necessary to decrease the glass transition temperature to 0°C was approximately equal to the amount of non-freezable water in the hydrogels. These observations lead to the conclusion that the amount of non-freezable water cannot be explained by different types of water, but is based either on a restriction of the diffusion of water in hydrogels or on a restriction of a further growth of ice crystals after transformation of the hydrogel from rubbery state (high flexibility of the polymer network) to glassy state (low flexibility of the polymer network).

A high resolution NMR investigation into the microstructure of HEMA and EEMA copolymers

13C NMR spectra (125 MHz) of 2-hydroxyethyl methacrylate (HEMA) and 2-ethoxyethyl methacrylate (EEMA) copolymers, prepared by bulk free radical copolymerisation, were analysed in terms of the comonomer composition and relative stereochemical configuration. The monomer reactivity ratios were evaluated using a nonlinear least squares analysis, considering both the terminal and penultimate models. Although both models adequately describe the experimentally determined copolymer compositions at a 99.5% confidence level or better, the statistical F-test showed that there is no significant improvement in the fit of the data for the penultimate model over that for the terminal model. The best estimates for the terminal model reactivity ratios are rH = 1.202 and rE = 0.724. The copolymers were found to be mainly syndiotactic. Using the Bernoullian distribution of stereoregularity, the coisotacticity parameters ΘHH = 0.25, ΘEE = 0.23 and Θ* = ΘHE = ΘEH = 0.21 were determined. Predictions for stereochemical and comonomer distributions in a copolymer prepared to high conversions are presented.

Photo-crosslinked copolymers of 2-hydroxyethyl methacrylate, poly(ethylene glycol) tetra-acrylate and ethylene dimethacrylate for improving biocompatibility of biosensors

A copolymer containing 88% 2-hydroxyethyl methacrylate (HEMA), 9% poly(ethylene glycol) (MW 18.5 kDa) tetra-acrylate and 3% ethylene dimethacrylate was prepared and evaluated for use as a biocompatible interface between glucose biosensors and tissue in the rat. The glucose sensor utilizes glucose oxidase that is electrically ‘wired’ to a gold current collector by a reduction-oxidation polymer. Coatings of the copolymer were crosslinked in situ on the sensors using long wavelength ultraviolet light and 2,2-dimethoxy-2-phenyl-acetophenone as the initiator. The effect these films had on the current response to glucose was measured. Over a glucose concentration range of 0–30 mM, the average percentage decrease in response was 45 ± 28% (mean ± 95% confidence interval) at 37 °C for films that were about 0.1 mm thick, an acceptable value. Copolymer-treated and control electrodes were implanted in the intrascapular subcutaneous tissue of male Sprague-Dawley rats for three days. The explanted samples were evaluated using scanning electron microscopy. The control electrodes were highly encapsulated with fibrous material, while the copolymer-treated electrodes induced much less encapsulation. The results show this copolymer to be a candidate as a biocompatible coating for electrically wired oxidoreductase-based subcutaneous biosensors.

USA—Improved biocompatibility of biosensors : In BIOMATERIALS (16/5 (389–396) 1995) C.P. Quinn, C.P. Pathak, A. Heller and J.A. Hubbell of The University of Texas report on “Photo-crosslinked copolymers of 2-hydroxyethyl methacrylate, poly(ethylene glycol) tetra-acrylate and ethylene dimethacrylate for improving biocompatibility of biosensors”

USA—Improved biocompatibility of biosensors : In BIOMATERIALS (16/5 (389–396) 1995) C.P. Quinn, C.P. Pathak, A. Heller and J.A. Hubbell of The University of Texas report on “Photo-crosslinked copolymers of 2-hydroxyethyl methacrylate, poly(ethylene glycol) tetra-acrylate and ethylene dimethacrylate for improving biocompatibility of biosensors”

Characterization of colon-specific azo polymers: A study of the swelling propertoes and the permeability of isolated polymer films

In order to prepare azo polymers for colonic targeting, copolymers of 2-hydroxyethyl methacrylate (HEMA) and methyl methacrylate (MMA), and terpolymers of HEMA, MMA, and methacrylic acid (MA) were synthesized in the presence of different azo compounds. In the present study, the azo polymers were characterized by swelling and permeability studies, performed on isolated films. It was shown that MMA is the swelling capacity and rate determining compound in the azo polymers investigated. Permeability experiments revealed that the diffusion of caffeine as well as the transmission of water vapour is proportional to the concentration of HEMA in the polymers. Hydrophilic plasticizers increase water vapour transmission and diffusion of caffeine through the films. By incorporation of MA into the azo polymers, pH dependency was introduced. The swelling behaviour and diffusion of caffeine are nearly constant over the pH range from 1 to 6. A sharp increase above pH 6, corresponding with the ionization of the carboxylic acid groups appears, with a maximum around pH 8.

Application of new coatings for vascular grafts based on polyacrylic systems with antiaggregating activity

A study has been made of the behaviour of knitted and woven Dacron mesh used in the preparation of vascular grafts when coated with either a layer of poly(2-hydroxyethyl methacrylate) or co-polymers of 2-hydroxyethyl methacrylate with 5, 10 or 20 wt% of an acrylic derivative of salicylic acid, 2-methacryloyloxybenzoic acid. In vitro studies were carried out to quantify the loss of polymer under flow conditions, and ex vivo studies were done in dogs to quantify the deposition of 111ln-oxinelabelled platelets. The treated materials showed a lesser deposition of platelet thrombi when compared with the control group. Biomaterials (1994) 15, (10) 759–765

Microstructural analysis of copolymers of hydroxyethylmethacrylate and methacrylic esters of biomedical interest by n.m.r. spectroscopy

Copolymers of N-(4-methacryloyloxyphenyl), 2-(4-methoxyphenyl) acetamide, M, a methacrylic derivative of 4-methoxyphenylacetic acid, and 2-hydroxyethylmethacrylate, H, prepared by free-radical polymerization in solution at low conversion, were analysed by 1H (300 MHz) and 13C (75.5 MHz) nuclear magnetic resonance spectroscopy, in terms of sequence distribution and stereochemistry of monomeric units along the copolymer chains. The concentration of M- and H-centred sequences was determined experimentally from the analysis of the α-CH 3 resonance signals of M and H units, which gave a relatively complex pattern assigned to M and H centred triads with specific composition and stereochemical configuration. The carbonyl carbon group of M and H gave resonance signals with different chemical shift sensitive to sequences of tactic pentads, independently of the chemical composition. The experimental results were in fairly good agreement with those calculated statistically, taking into consideration the terminal copolymerization model and Bernoullian distribution of stereoregularity, with the statistical parameters P ij and P ii determined from the reactivity ratios r M=1.49 and r H=0.61 and the stereochemical parameters σ MM=0.27, σ HH=0.21 and σ∗=σ MH =σ HM =0.30 .

Strong buffering characteristics and swelling behavior of cationic copolymers

AbstractThe swelling behavior of crosslinked cationic copolymers of 2‐hydroxyethyl methacrylate with (3‐methacryloylamino propyl) trimethylammonium chloride was investigated in various buffered solutions as a function of ionic strength and pH. The equilibrium degree of swelling increased as the pH decreased or as the cationic group‐containing comonomer in the polymer increased. The water transport in such copolymers was controlled by a non‐Fickian mechanism. These results can be used in the development of physiologically sensitive controlled drug delivery systems. © 1994 John Wiley & Sons, Inc.

Studies on graft copolymerization of 2‐hydroxyethyl methacrylate onto poly(vinyl chloride)

AbstractPoly(vinyl chloride) was dehydrochlorinated in alkali solution and then grafted with 2‐hydroxyethyl methacrylate (HEMA) using benzoyl peroxide as a free‐radical initiator under a nitrogen atmosphere. The investigations involved examining the effects of grafting efficiency on various conditions, such as degree of dehydrochlorination, HEMA concentration, solvent effect, and reaction time. Maximum grafting to the extent of 57.2% was obtained. The mixed solvent grafting was attempted. © 1994 John Wiley & Sons, Inc.

Photoinduced graft copolymerization of 2‐hydroxyethyl methacrylate on cotton cellulose in the presence of triethyleneglycol dimethacrylate

AbstractThe addition of a bifunctional monomer, triethylene glycol dimethacrylate (TEGDMA), to a grafting system containing 2‐hydroxyethyl methacrylate (HEMA) and benzoin ethyl ether photoinitiator substantially increased the graft add‐on of the unswollen and sodium hydroxide–swollen cotton cellulose. Grafting caused changes in the properties of the substrate such as moisture regain, the water of imbibition, and the dyeability with a direct and a reactive dye in accordance with the graft level. The observations have been explained in relation to structural changes in the grafted cotton. © 1994 John Wiley & Sons, Inc.