Living radical polymerization of n-butyl acrylate was achieved by single electron transfer/degenerative-chain transfer mediated living radical polymerization in water catalyzed by sodium dithionate. The plots of number-average molecular weight versus conversion and ln[M] 0 /[M] versus time are linear, indicating a controlled polymerization. This methodology leads to the preparation of a,x-di(iodo) poly (butyl acrylate) (a,x-di(iodo)PBA) macroinitiators. The influence of polymerization degree ([monomer]/[initiator]), amount of catalyst, concentration of suspending agents and temperature were studied. The molecular weight distributions were determined using a combination of three detectors (TriSEC): right-angle light scattering (RALLS), a differential viscometer (DV), and refractive index (RI). The methodology studied in this work represents a possible route to prepare well-tailored macromolecules made of butyl acrylate in an environmental friendly reaction medium. Moreover, such materials can be subsequently functionalized leading to the formation of different block copolymers of composition ABA.

The synthesis of a block copolymer poly(vinyl chloride)-b-poly(n-butyl acrylate)-b-poly(vinyl chloride) is reported. This new material was synthesized by single-electron-transfer/degenerative-chain-transfer-mediated living radical polymerization (SET-DTLRP) in two steps. First, a bifunctional macroinitiator of a,x-di(iodo)poly (butyl acrylate) [a,x-di(iodo)PBA] was synthesized by SET-DTLRP in water at 25 8C. The macroinitiator was further reinitiated by SET-DTLRP, leading to the formation of the desired product. This ABA block copolymer was synthesized with high initiator efficiency. The kinetics of the copolymerization reaction was studied for two PBA macroinitiators with number-average molecular weight of 10 k and 20 k. The relationship between the conversion and the number-average molecular weight was found to be linear. The dynamic mechanical thermal analysis suggests just one phase, indicating that copolymer behaves as a single material with no phase separation. This methodology provides the access to several block copolymers and other complex architectures that result from combinations of thermoplastics (PVC) and elastomers (PBA). From industrial standpoint, this process is attractive, because of easy experimental setup and the environmental friendly reaction medium. V V C 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: [3001][3002][3003][3004][3005][3006][3007][3008] 2006

Abstract:The biocompatibility of chemoenzymatically generated dextran-acrylate hydrogels has been evaluated in vitro, using human foreskin fibroblasts, and in vivo, by subcutaneous and intramuscular implantation in Wistar rats for up to 40 days. In vitro tests show that hydrogel extracts only minimally reduced (Ͻ10%) the mitochondrial metabolic activity of fibroblasts. Direct contact of the hydrogels with cells induced a cellular proliferation inhibition index (CPII) of 50 -80%, compared with a control, whereas through indirect contact, the CPII values were Ͻ16%, suggesting that the high CPII values achieved in the direct assay test were likely due to mechanical stress or limitations in oxygen diffusion. Hence, the hydrogels were noncytotoxic. Moreover, cellmaterial interaction studies show that these hydrogels were nonadhesive. Finally, histologic evaluation of tissue response to subcutaneous and intramuscular implants showed acceptable levels of biocompatibility, as characterized by a normal cellular response and the absence of necrosis of the surrounding tissues of the implant. In the first 10 days, the foreign-body reaction in the intramuscular implantation was more severe than in subcutaneous implantation, becoming identical after 30 days. In both cases, dextran hydrogels did not show signs of degradation 6 weeks postimplantation and were surrounded by a thin fibrous capsule and some macrophages and giant cells. This response is typical with a number of nondegradable biocompatible materials. These results indicate that dextran hydrogels are biocompatible, and may have suitable applications as implantable longterm peptide/protein delivery systems or scaffolds for tissue engineering.

The aim of this work is to the study the influence of the isomer structures of butyl acrylate monomer on the single-electron transfer/degenerative chain transfer mediated living radical polymerization (SET-DTLRP). The kinetic of isobutyl acrylate is determined for the first time by SET-DTLRP in water catalyzed by sodium dithionite. The plots of number-average molecular weight versus conversion and ln([M] 0 /[M]) versus time are linear, demonstrating a controlled polymerization. The influence of the isomer t-butyl, i-butyl, and n-butyl on the kinetics, properties, and stereochemistry of the reactions was assessed. To the best of our knowledge, there is no previous report dealing with the synthesis of PiBA by any LRP approach in aqueous medium. The results presented in this work suggest that the stability provided by the acrylate side group has an important influence in the polymerization process.

Abstract:It is well known that hydrogels can be suitable for biomedical, agricultural, and industrial applications. In particular, they have been widely used for the preparation of drug-delivery systems. The preparation and characterization of such a system should be useful for introducing students to these materials. This paper describes the preparation of polyacrylamide hydrogels having different crosslinking densities from the view of optimizing this system for acetylsalicylic acid (aspirin) release. The observations of equilibrium swelling, solute transport, and thermal analysis are related to the network structure of polyacrylamide hydrogel.