Chemically cross-linked hydrogels constitute a novel injectable tissue engineering material. At present, one of the key problems is to find an appropriate initiator. This study evaluated the cytotoxicity in vitro of a water-soluble redox initiating system consisting of ammonium persulfate (APS) and N, N, N′, N′-tetramethylethylenediamine (TEM- ED). Gelation time of PEG diacrylate macromer in phos- phate buffer saline solution was first adjusted to guarantee that the examined initiator concentrations are sufficiently high to trigger polymerization of macromers. NIH/3T3 fi- broblasts were employed to examine cytotoxicity via MTT measurements and optical microscopic observations. It has been found that the combined APS/TEMED system exhibits negative cooperative effect, for the underlying cytotoxicity is even lower than that of APS or TEMED at certain concen- trations.
Free radical polymerization and living ion polymerization have been simulated via the dynamic Monte Carlo method with the bond-fluctuation model in this paper. The polymeriza-tion-related parameters such as conversion of monomers, degree of polymerization, average molecular weight and its distribution are obtained by statistics. The simulation outputs are con-sistent with the corresponding theoretical predictions. The scaling relationships of the coil size versus chain length are also confirmed at different volume fractions. Furthermore, the effect of diffusion on polymerization is revealed preliminarily in our simulation. Hence the simulation ap-proach has been proven to be feasible to investigate polymerization reactions with the advan-tages that configuration and diffusion of polymer chains can be examined together with polym-erization kinetics.
Lü Wenqi & DING Jiandong Key Laboratory of Molecular Engineering of Polymers, Department of Macromolecular Science, Fudan University, Shanghai 200433, China
A novel biodegradable and thermosensitive microgel particle was prepared via suspension polymerization of a well-designed biodegradable macromonomer. The macromonomer is composed of amphiphilic block copolymer PEO-PPO-PEO, oligo(ester) and acryloyl end groups. Ammonium persulfate was employed as the initiator and N,N,N′,N′-tetramethylethylene-diamine as the accelerator. The resultant hydrogel particles were confirmed to be reversely thermosensitive as well as biodegradable.
