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The effects of synthesis‐solvent composition, initiator concentration, comonomer type and monomer purity on the volume swelling ratios, and polymer‐solvent interaction parameter χ have been investigated as a function of temperature. Non‐ionic N‐isopropylacrylamide (NIPAAM) homopolymer gels, poly[NIPAAM‐co‐(dimethyl itaconate)] (P(NIPAAM‐co‐DMI)) and poly[NIPAAM‐co‐(itaconic acid)] (P(NIPAAM‐co‐IA)) gels containing hydrophobic (DMI) and hydrophilic (IA) comonomers were prepared by free radical polymerization using potassium persulfate (KPS) –N, N, N′, N′‐tetramethyl ethylene diamine (TEMED) (redox initiator) in the presence of an N, N′‐methylene bis(acrylamide) (MBAAM) cross‐linking agent. The synthesis‐solvent composition (40/60 mixture of water/methanol and water) and initiator concentration employed significantly affected the properties of the NIPAAM gels. The transition temperatures of P(NIPAAM‐co‐IA) gels synthesized in water/methanol mixture were higher than that of the gel obtained in water. Furthermore, χ values of the NIPAAM homopolymer gel prepared with higher KPS content was an increasing function of temperature, while χ values of the sample obtained with lower initiator concentration changed around a critical solubility value 0.50. The results obtained also show that the interactions between monomer and solvent molecules in the reaction media (ie composition of the pregel solution) have an important effect on the formation and properties of the network structure (ie pore sizes of the gels). © 2000 Society of Chemical Industry

Temperature‐ and pH‐sensitive copolymers and terpolymers of N‐isopropylacrylamide (NIPAAm) with itaconic acid (IA), monomethyl itaconate (MMeI), monobutyl itaconate (MBuI), monooctyl itaconate (MOcI), monocetyl itaconate (MCeI), and dimethyl itaconate (DMI) were prepared by free radical solution polymerization method. The dependence of coil‐to‐globule transition on pH and composition, molecular structures, and reactivities of monoalkyl itaconates, molecular weight distributions, and glass transition temperatures of copolymers and terpolymers were investigated using FT‐IR and UV–visible spectroscopic techniques, gel permeation chromatography (GPC), differential scanning calorimetry (DSC), and acid–base titration methods. The temperature‐/pH‐dependent coil‐to‐globule transition measurements showed that, upon increasing the content and length of alkyl chains, the lower critical solution temperatures (LCSTs) were shifted to higher temperatures. This meant that with increase in the length of hydrophobic alkyl chain in the monoitaconates intramolecular intreactions between the carboxyl groups were suppressed and LCSTs increased. The aqueous solution behaviors of NIPAAm/IA/DMI terpolymers also revealed that, even if the terpolymer hydrophobicity is increased by adding DMI units, the presence of IA units overcame the decrease in hydrophilicity of the terpolymers. The presence of DMI units in the terpolymers balanced the hydrophilic character of IA. DSC results supported the ones obtained from the pH‐dependent coil‐to‐globule transition measurements. An increase in both the chain length of alkyl groups attached to the monoitaconates and the contents of the mono‐ and dialkyl itaconates in the copolymers and terpolymers decreased the Tgs. In the case of NIPAAm/IA and NIPAAm/MMeI copolymers, the presence of the carboxyl groups forming hydrogen bonds increased the Tg, while the monoalkyl and dialkyl itaconates such as MBuI, MOcI, MCeI and DMI lead to a decrease in Tg of copolymers and terpolymers because of the suppression of intramolecular interactions (resulting from the COOH and COO− groups) through the longer alkyl spacers. The dependence of the thermosensitivity of these NIPAAm copolymers and terpolymers on different conditions of pH, and the nature and content of comonomers suggests that they can be useful in biotechnology and drug delivery applications which involve small changes in pH and temperature. Copyright © 2009 John Wiley & Sons, Ltd.

Block copolymers containing segments of poly(dimethylsiloxane) (PDMS) and polystyrene were synthesized. Dihydroxy terminated PDMS Mn 2500 g/mol, was reacted with an ali‐phatic diisocyanate (isophorone diisocyanate) and an aliphatic hydroperxide (t‐butyl hy‐droperoxide). The resulting polymeric peroxycarbamate having siloxane units (a new mac‐roinitiator) was used as free radical initiator for vinyl polymerization of styrene. Formation of block copolymers was illustrated by several characterization methods such as chemical and spectroscopic analysis, fractionation, and GPC. Mechanical and thermal characterization of the copolymers were made by stress–strain tests and DSC. The surface properties and the morphology of the block copolymers were investigated by contact angle measurements and SEM. © 1996 John Wiley & Sons, Inc.

Controlled-release buccoadhesive tablets containing pindolol were prepared and evaluated in order to achieve constant plasma concentrations during the treatment of chronic hypertension and to improve the bioavailability of pindolol by the avoidance of hepatic first-pass metabolism. The formulations were tested for weight, hardness, friability, content uniformity, swelling rate, bioadhesive force, and drug release rate values. Carbopol 934 and NaCMC were used as bioadhesive polymers and Methocel K4M, Methocel K15M, and HPC were added as matrix-forming polymers.

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SynopsisBlock copolymers containing segments of poly (ethylene oxide) and polystyrene were synthesized. Dihydroxyl-terminated polyethers (PEG-4000 and PEG-20,000) were reacted with a n aliphatic diisocyanate (3-isocyanatomethyl-3,5,5-trimethyl-cyclohexyl-isocyanate) and with a n aliphatic hydroperoxide ( t-butyl hydroperoxide 1. The resulting polymeric peroxycarbamates were used as free radical initiators for vinyl polymerization. Formation of block copolymers was illustrated by several characterization methods such as chemical and LJV analysis, infrared spectroscopy, and DSC thermograms. Mechanical characterization of the copolymers was made on the basis of the stress-strain curves obtained from a mechanical testing instrument (Tensilon) . INTRODUCTIONThe potential of block copolymers has begun to be appreciated after the development of polyurethanes. The preparation of linear polyurethanes composed of soft polyester segments and hard polyurethane sequences was reported 30 years ago.' The synthesis of well-defined block copolymers from the point of view of molecular architecture was secured after the development of controlled living-anionic polymerization techniques.2 An extensive review of block copolymer synthesis covering various procedures including coupling reactions between the segments containing adequate functional groups was p~b l i s h e d .~ Recently various oligomers, copolymers, and interpenetrating networks have been prepared by using prepolymers of diols, diisocyanates, hydroperoxides, and azo-compounds containing functional groups.4-" A project concerning a new type of block copolymer synthesis was carried out in our laboratories. It is based on the chemical combination of low molecular weight inherently soft, rubbery polymers such as propylene oxide, with thermoplastic polymers of basically glassy properties such as polystyrene or a similar vinyl polymer. Several papers were published to describe various modes of preparation and characterization of' these block copolymer^.'^-'^ The copolymers were prepared by using two different procedures. In the stepwise procedure, a polymeric peroxycarbamate or a diperoxycarbamate was first prepared. This intermediate product was subsequently used to initiate the polymerization of a vinyl monomer at elevated temperatures. In the other procedure, peroxycarbamates were synthesized using the vinyl monomer as the solvent. The mixture was then heated in order to obtain the copolymer.In this work, copolymers of styrene and ethylene oxide were prepared by using the stepwise polymerization technique. For this purpose, commercially available low and high molecular weight dihydroxyl-terminated prepolymers were first end-capped with an aliphatic &isocyanate. The resulting intermediates were then reacted with an aliphatic hydroperoxide. The diperoxycarbamates prepared according to the preceding stepwise procedure were used as the free radical initiator for styrene polymerization.The copolymers were characterized by physical methods and by mechanical and thermal analysi...