Degradation of poly(D,L‐lactic acid)‐b‐poly(ethylene glycol)‐b‐poly(D,L‐lactic acid) copolymer by electron beam radiation

Abstract

This article investigates the effects of electron beam (EB) radiation on poly(D,L-lactic acid)-b-poly (ethylene glycol) copolymer (PLA-b-PEG-b-PLA). The copolymer films were EB irradiated at doses from 0 to 100 kGy. The degradation of these films was studied by measuring the changes in their molecular weight, mechanical and thermal properties. The dominant effect of EB radiation on PLA-b-PEG-b-PLA is chain-scission. With increasing irradiation dose, recombination reactions or partial crosslinking may occur in addition to chain scission. The degree of chain scission G s and crosslinking G x of sample are calculated to be 0.213 and 0.043, respectively. A linear relationship is also established between the decreases in molecular weight with increasing irradiation dose. Elongation at break of the irradiated sample decreases significantly, whereas its tensile strength decreases slightly. The glass transition temperature (T g ) is basically invariant as a function of irradiation dose. Thermogravimetric analysis shows that its thermal stability decreases with increasing dose.

Size-Controlled Nanomicelles of Poly(lactic acid)–Poly(ethylene glycol) Copolymers with a Multiblock Configuration

“…Baick et al reported the reversible oligomerization of L-lactic acid in this binary catalyst system [24]. Miao et al applied this binary catalyst method to the synthesis of PLA-PEG-PLA triblock copolymers [25]. The reaction time, temperature, pressure and ratio of binary catalysts were studied to determine their effect on polymer decomposition, discoloring and racemization [14][15][16]24,25].…”

“…Miao et al applied this binary catalyst method to the synthesis of PLA-PEG-PLA triblock copolymers [25]. The reaction time, temperature, pressure and ratio of binary catalysts were studied to determine their effect on polymer decomposition, discoloring and racemization [14][15][16]24,25]. We previously reported that a reaction time longer than 20 h in melt polycondensation of PLLA was ineffective for further polymerization, but rather induced discoloration and racemization of PLLA [14].…”

On the Mechanisms of the Effects of Ionizing Radiation on Diblock and Random Copolymers of Poly(Lactic Acid) and Poly(Trimethylene Carbonate)

“…Although some data on the effects of electron-beam (EB) irradiation on PLA and its copolymers have been published [38,39,40], no studies have been reported so far regarding the effects of radiation on the properties of PLA- co -PTMC copolymers. In the present work, chemical changes occurring upon irradiation of diblock and random copolymers of various molar compositions were investigated.…”

Drug Release From Irradiated PLGA and PLLA Multi-Layered Films

“…Previously, electron beam (e-beam) radiation has been shown to modify the physical properties of PLGA and PLLA and their copolymers, 26 upon which tunable hydrolysis rates from these polymers can be achieved. 27,28 Preliminary drug release results from these irradiated polymer films also show that radiation accelerates the onset (or reduces the lag phase) of drug release from these bulk degrading polymers (results not published).…”