Controlled in vitro degradation behavior of highly oriented long‐chain‐branched poly(lactic acid) produced by solid‐phase die drawing

Abstract

Highly oriented long‐chain‐branched poly(lactic acid) (LCB‐PLA) was fabricated through solid‐phase die drawing technology, and the in vitro degradation behavior of the oriented samples in phosphate‐buffered saline (PBS) was studied. During degradation, the weight retention and molecular weight for both PLA and LCB‐PLA increased with the increase of draw ratio. Moreover, the degradation autocatalytic effect was delayed, and the deterioration of mechanical strength was reduced by orientation, which was beneficial for controlling the degradation degree and decay rate of strength for PLA as bone fixation materials. The influence mechanism of orientation on the in vitro degradation of PLA was explored. The degradation of PLA in PBS was ascribed to the hydrolytic degradation of ester bonds on the molecular chain. By orientation, a dense microfibrillar crystalline structure formed both on the surface and inside of PLA samples, limiting the diffusion and absorption of PBS molecules into the PLA matrix effectively, inhibiting the hydrolytic degradation of ester bonds, and thus delaying the deterioration of mechanical properties of PLA. © 2019 Wiley Periodicals, Inc. J Biomed Mater Res Part A, 2019.

Biocompatibility improvement and controlled in vitro degradation of poly (lactic acid)‐b‐poly(lactide‐co‐caprolactone) by formation of highly oriented structure for orthopedic application

“…Furthermore, the FT‐IR spectra of isotropic samples during degradation were normalized based on absorption peak at 1454 cm −1 . As depicted in Figure 8C–F, for both PLA and PLA‐b‐PLCL, the intensity of absorption peak at 1750 cm −1 assigned to CO decreased with increasing degradation time, while the intensity of absorption peak at 3298 cm −1 attributed to –OH increased obviously, indicating the hydrolytic of ester groups into carboxyl and hydroxyl groups during degradation 41 . By introduction of PLCL segments, the hydrolytic degradation mechanism of PLA remained unchanged.…”

Construction of a Highly Oriented Poly(lactic acid)-Based Block Polymer Foam and Its Self-Reinforcing Mechanism

“…Polymer foams, like polystyrene, polypropylene, polyurethane, etc., which possess properties of lightweight, high specific strength, and energy absorption, are widely applied in the fields of packaging, building, transportation, etc. However, the difficulty in their degradation and recycling brings about a petrochemical energy crisis and ecological environment problems, while biodegradable polymer foams have attracted widespread attention. − Poly­(lactic acid) (PLA), as a biodegradable aliphatic polyester, is considered as the most promising sustainable substitute for petroleum-based polymers due to its superior mechanical properties, biocompatibility, and processing ability. − Supercritical CO 2 (sc-CO 2 ) batch foaming is an efficient way to prepare PLA foams. , Nevertheless, PLA exhibits low viscoelasticity at the processing temperature due to its linear structure and slow crystallization kinetics, negatively affecting cell growth and uniformity in the foaming process . In recent times, some methods have been developed to improve the foaming behavior of PLA, including chain extension, , incorporation of nucleators or nanoparticles, − blending with other polymer materials, etc. − But the abovementioned approaches failed to significantly improve the mechanical properties of PLA foams.…”

Highly Reinforced Poly(lactic acid) Foam Fabricated by Formation of a Heat-Resistant Oriented Stereocomplex Crystalline Structure

“…Polymer foams, like polyurethane foams and polystyrene (PS) foams, are extensively used in building, packaging, and transportation fields attributed to their light weight, insulation, and energy absorption. However, overuse of such petroleum-based polymers brings about both the petrochemical energy crisis and ecological environment problems due to difficulty of degradation and recycling. − Poly­(lactic acid) (PLA), as a biodegradable aliphatic polyester derived from renewable resources, exhibits superior mechanical properties and processing ability. − However, poly­( l -lactide) (PLLA) shows low viscoelasticity at the processing temperature due to poor crystallization ability, negatively influencing cell growth and cell uniformity during the foaming process. Currently, some methods were developed to improve the cell structure and mechanical properties of the PLLA foam, which include forming a branched chain structure, , improving the molecular weight, , polymer blending, incorporation of nanoparticles or nucleators, and so forth. − However, the aforementioned approaches may compromise the biocompatible and biodegradable nature of the PLLA foam and could not significantly improve its mechanical properties.…”