The Infona portal uses cookies, i.e. strings of text saved by a browser on the user's device. The portal can access those files and use them to remember the user's data, such as their chosen settings (screen view, interface language, etc.), or their login data. By using the Infona portal the user accepts automatic saving and using this information for portal operation purposes. More information on the subject can be found in the Privacy Policy and Terms of Service. By closing this window the user confirms that they have read the information on cookie usage, and they accept the privacy policy and the way cookies are used by the portal. You can change the cookie settings in your browser.
Graft copolymerization of mixtures of 2-hydroxyethyl methacrylate (HEMA) with n-butyl methacrylate (BMA) onto soluble gelatin was attempted using ceric ammonium nitrate as initiator, with the aim of obtaining hydrogels based on two different components: a natural polymer and a synthetic polymer. Other hydrogels were formed by simultaneous graft copolymerization and crosslinking using ethylene glycol...
Poly(vinyl alcohol) (PVA) hydrogels were prepared by quenching solutions containing PVA polymer in pure water or an aqueous solution of dimethylsulfoxide (DMSO). Remarkably different PVA hydrogels were obtained by varying processing parameters, i.e. DMSO concentration, initial PVA concentration and quench temperature. The bulk structure of PVA hydrogels was investigated by scanning electron microscopy...
Poly(diethylaminoethyl methacrylate-co-hydroxyethyl methacrylate), poly(diethylaminoethyl acrylate-co-hydroxyethyl methacrylate) and poly(methacrylaminopropyl ammonium chloride-co-hydroxyethyl methacrylate) were synthesized by free radical polymerization and characterized using differential scanning calorimetry and dynamic mechanical analysis. Transport of citrate-phosphate-borate buffer solutions...
Solutions of a 15-mer of poly(vinyl alcohol) in water, ethanol and a 11 (mole fraction) mixture of water and ethanol have been studied by molecular dynamics simulations. The solvent structure near the solute is analysed in terms of radial distribution functions and hydrogen bonding. Results indicate a preferential solvation by water molecules. Hydrogen-bond life time analysis shows that solvent-solute...
Protonic transport in polyacrylamide hydrogels doped with H 3 PO 4 or H 2 SO 4 has been studied using impedance spectroscopy, Fourier transform infra-red (FT i.r.) and differential scanning calorimetry (d.s.c.) techniques. These hydrogels exhibit room temperature conductivities greater than 10 -2 S cm -1 ; these increase with temperature to...
Cross-linked films of copolymers of 2-hydroxyethyl methacrylate (HEMA) and triethylenglycol dimethacrylate (TEGDMA) were prepared by free radical polymerization initiated at 60°C. The swelling behaviour of films prepared with 2, 5 and 10 mol% of TEGDMA was followed gravimetrically and the diffusion coefficients were determined according to the Fickian law at several temperatures in the interval 25-50°C...
Copolymers of furfuryl methacrylate (F) and N,N-dimethyl acrylamide (A) were prepared by free radical photoinitiated polymerisation in bulk at 40°C, using 2,2-azobisisobutyronitrile (AIBN) as photoinitiator. The reactivity ratios of both monomers (r F and r A ) were determined according to the general copolymer composition equation by applying the Tidwell and Mortimer non-linear least...
Prediction of swelling behaviour of hydrogels containing diprotic acid moieties, sensitive to pH and ionic strength changes of the swelling medium, was investigated. The equations derived for the prediction of the theoretical swelling curves are based on the phantom network theory of Erman et al. and the approaches of Peppas et al. For all predictions, a number of polymer-based parameters, solution...
Proton transverse relaxation time (T 2 ) and molecular self-diffusion coefficient (D) n.m.r. measurements of water in three hydrogels based on poly(2-hydroxyethyl-methacrylate) (pHEMA) have been performed in order to investigate the state of water and its interaction with the polymer network. Measured T 2 values are discussed and quantitatively interpreted by assuming the chemical...
Proton-conducting poly(acryl amide) hydrogels are prospective materials for application in electrochemical devices working at ambient temperatures. In the present paper, the conducting properties of hydrogels doped with H 3 PO 4 or H 2 SO 4 are analysed in connection with such features of the hydrogel membrane as sorption and permeation of solvents and tensile strength...
This study has examined balanced and unbalanced polyampholyte hydrogel swelling transitions as a function of total polymer ion and bath salt concentration. The total polymer ion concentration ranged from 0 to 1.4M and the bath salt concentration from 1μM to 1M. Polyampholyte swelling transitions were studied experimentally using hydrogels with varying proportions of acryl-amido methyl propylsulfonic...
Thermally responsive hydrogels of N-isopropylacrylamide containing hydrophobic comonomers were synthesized by free radical polymerization in both toluene and water. Various hydrophobic monomers were used, i.e. methyl methacrylate, hexylacrylate, hexafluoroisopropylmethacrylate and hexafluorobutylmethacrylate. Also polymers containing hydrophilic methacrylic acid were synthesized. The swelling properties...
1,6-Bis-3-(vinyl-3-2-pyrrolidonyl)hexane (BNVP) was synthesized for use as a crosslinker in the photopolymerization of 1-vinyl-2-pyrrolidone (NVP). A model compound, 3-hexyl-1-vinyl-2-pyrrolidone (HNVP), was also synthesized for use as a model comonomer in the kinetic studies of NVP copolymerization. Copolymerizations with NVP and low feed ratios of HNVP indicate that alkyl substitution in the 3-position...
Proton Magnetic Resonance (PMR) Imaging has been used to study the volume-phase-transition in a thermoreversible gel. This is demonstrated in the LCST polymer poly(N-isopropylacrylamide), swollen in water. The volume-phase-transition is conveniently monitored through one-dimensional proton images. PMR images, derived from relaxation and diffusion weighted planar spin-echo experiments, provide insights...
The determination of porous structure of fragile materials from classical methods such as mercury porosimetry and nitrogen adsorption-desorption methods is often delicate and can be source of false structure interpretation. The thermoporometry is an alternative method, sometimes the unique method, allowing a better characterization of porous fragile and soft materials and hydrogels.In this paper we...
A series of strong polyelectrolyte hydrogels based on acrylamide and 2-acrylamido-2-methylpropane sulfonic acid sodium salt or [(Methacrylamido)propyl]trimethyl ammonium chloride were prepared by free-radical crosslinking copolymerization. Their swelling behavior was investigated in a good solvent (water), in polymer melt and in aqueous polymer solutions. Poly(ethylene glycol) of various molecular...
The behaviour of deswollen (D) and equilibrium swollen (S) non-ionic poly(N-isopropylacrylamide) (PNIPA) hydrogel samples in aqueous hydroxides and chlorides of Na and K are investigated. The samples respond in dramatically different styles to increasing concentrations of the additive in the external aqueous medium. Both samples exhibit volume phase transition at additive concentrations characteristic...
Novel amphiphilic alternating multiblock copolymers were synthesized by the polycondensation reaction of α,ω-dihydroxypoly(2-ethyl-2-oxazoline) (HO-PEtOz-OH) with α,ω-dicarboxypoly( -caprolactone) (HOOC-PCL-COOH) by varying the block composition. The phase transition and swelling behaviors of multiblock copolymer hydrogels depending on temperature changes were investigated in aqueous media. The crystalline...
Poly(vinyl alcohol) was modified with pendent acrylate groups to form a macromer that was crosslinked via photopolymerization. Polymerization behavior was studied for several initial macromer concentrations using DSC and Near-IR spectroscopy. Under mild photoinitiating conditions (e.g. 0.05wt% initiator and less than 20mW/cm2 of 365nm light), the hydrogels polymerized to 100% conversion in less than...
A series of hydrophilic model networks based on homopolymers of a weak base were prepared using group transfer polymerization (GTP) and characterized in terms of their aqueous degree of swelling as a function of pH. This constitutes the first reported example of cationic hydrogels in which the length of segments between cross-links is kept constant. The synthesis involved the GTP of 2-(dimethylamino)ethyl...
Set the date range to filter the displayed results. You can set a starting date, ending date or both. You can enter the dates manually or choose them from the calendar.