title: The effects of molecular structure on sol-to-gel transition of biodegradable poly(depsipeptide-co-lactide)-g-PEG copolymers.
abstract: We report on the effects of number and length of PEG chains in poly(depsipeptide-co-dl-lactide)-g-poly(ethylene glycol) (P(DG-dl-LA)-g-PEG) copolymers on their sol-to-gel transition behavior. The graft-type copolymer is suitable for the systematic study of the effects of molecular structure and hydrophilic/hydrophobic balance on its sol-to-gel transition. We prepared various P(DG-dl-LA)-g-PEG copolymers through coupling reactions between the pendant carboxylic acid groups of P(GD-dl-LA) and the end hydroxyl group of MeO-PEG having various molecular weights. Temperature-responsive sol-to-gel transition of the obtained copolymer solution in phosphate-buffered solution (pH 7.4, ionic strength = 0.14) was investigated by the test tube inverting method and rheological measurements. P(GD-dl-LA)-g-PEG copolymer prepared from higher molecular weight PEG showed higher sol-to-gel transition temperatures compared with the copolymers prepared from lower molecular weight PEG, although these copolymers have similar weight content of PEG (23-24 wt.%). Similar trends were observed for groups of copolymers whose PEG contents were 27 or 30 wt.%. These results are informative for providing strategies on rational design of thermo-gelling polymers.
authors: a Faculty of Chemistry, Materials and Bioengineering, Department of Chemistry and Materials Engineering , Kansai University , 3-3-35 Yamate, Suita, Osaka 564-8680 , Japan.
authors: Akihiro
authors: A
authors: Takahashi
authors: Masaya
authors: M
authors: Umezaki
authors: Yasuyuki
authors: Y
authors: Yoshida
authors: Akinori
authors: A
authors: Kuzuya
authors: Yuichi
authors: Y
authors: Ohya
mesh_terms: D001672:Biocompatible Materials / Q000737:chemistry*; D047630:Depsipeptides / Q000737:chemistry*; D005782:Gels / Q000737:chemistry; D006863:Hydrogen-Ion Concentration; D057927:Hydrophobic and Hydrophilic Interactions; D044367:Phase Transition; D011092:Polyethylene Glycols / Q000737:chemistry*; D012212:Rheology; D013696:Temperature
chemical_list: D001672:Biocompatible Materials; D047630:Depsipeptides; D005782:Gels; C476738:poly(depsipeptide-co-lactide); D011092:Polyethylene Glycols