title: Surface Mechanical and Rheological Behaviors of Biocompatible Poly((D,L-lactic acid-ran-glycolic acid)-block-ethylene glycol) (PLGA-PEG) and Poly((D,L-lactic acid-ran-glycolic acid-ran-ε-caprolactone)-block-ethylene glycol) (PLGACL-PEG) Block Copolymers at the Air-Water Interface.
abstract: Air-water interfacial monolayers of poly((D,L-lactic acid-ran-glycolic acid)-block-ethylene glycol) (PLGA-PEG) exhibit an exponential increase in surface pressure under high monolayer compression. In order to understand the molecular origin of this behavior, a combined experimental and theoretical investigation (including surface pressure-area isotherm, X-ray reflectivity (XR) and interfacial rheological measurements, and a self-consistent field (SCF) theoretical analysis) was performed on air-water monolayers formed by a PLGA-PEG diblock copolymer and also by a nonglassy analogue of this diblock copolymer, poly((D,L-lactic acid-ran-glycolic acid-ran-caprolactone)-block-ethylene glycol) (PLGACL-PEG). The combined results of this study show that the two mechanisms, i.e., the glass transition of the collapsed PLGA film and the lateral repulsion of the PEG brush chains that occur simultaneously under lateral compression of the monolayer, are both responsible for the observed PLGA-PEG isotherm behavior. Upon cessation of compression, the high surface pressure of the PLGA-PEG monolayer typically relaxes over time with a stretched exponential decay, suggesting that in this diblock copolymer situation, the hydrophobic domain formed by the PLGA blocks undergoes glass transition in the high lateral compression state, analogously to the PLGA homopolymer monolayer. In the high PEG grafting density regime, the contribution of the PEG brush chains to the high monolayer surface pressure is significantly lower than what is predicted by the SCF model because of the many-body attraction among PEG segments (referred to in the literature as the "n-cluster" effects). The end-grafted PEG chains were found to be protein resistant even under the influence of the "n-cluster" effects.
authors.affiliation: School of Chemical Engineering, Purdue University , West Lafayette, Indiana 47907, United States.
authors.forename: Hyun Chang
authors.initials: HC
authors.lastname: Kim
authors.affiliation: School of Chemical Engineering, Purdue University , West Lafayette, Indiana 47907, United States.
authors.forename: Hoyoung
authors.initials: H
authors.lastname: Lee
authors.affiliation: School of Chemical Engineering, Purdue University , West Lafayette, Indiana 47907, United States.
authors.forename: Jawahar
authors.initials: J
authors.lastname: Khetan
authors.affiliation: School of Chemical Engineering, Purdue University , West Lafayette, Indiana 47907, United States.
authors.forename: You-Yeon
authors.initials: YY
authors.lastname: Won
mesh_terms: D000388:Air; D001672:Biocompatible Materials; D002208:Caproates / Q000737:chemistry*; D019855:Ethylene Glycol / Q000737:chemistry*; D005898:Glass / Q000737:chemistry; D057927:Hydrophobic and Hydrophilic Interactions; D019344:Lactic Acid / Q000737:chemistry*; D007783:Lactones / Q000737:chemistry*; D011092:Polyethylene Glycols / Q000737:chemistry*; D011098:Polyglactin 910 / Q000737:chemistry*; D011100:Polyglycolic Acid / Q000737:chemistry*; D000077182:Polylactic Acid-Polyglycolic Acid Copolymer; D012212:Rheology; D013499:Surface Properties; D014867:Water / Q000737:chemistry*
chemical_list: D001672:Biocompatible Materials; D002208:Caproates; D007783:Lactones; C102418:poly(lactic-glycolic acid)-poly(ethyleneglycol) copolymer; D014867:Water; D000077182:Polylactic Acid-Polyglycolic Acid Copolymer; D011100:Polyglycolic Acid; D019344:Lactic Acid; D011098:Polyglactin 910; D011092:Polyethylene Glycols; C121056:caprolactone; D019855:Ethylene Glycol