Biodegradable poly( L -lactic acid)–poly(ethylene glycol)–poly( L -lactic acid) (PLLA–PEG–PLLA) copolymers were synthesized by ring-opening polymerization of L -lactide using dihydroxy PEG as the initiator. The effects of different PEG segments in the copolymers on the mechanical and permeative properties were investigated. It was determined that certain additions of PEG result in composition-dependent microphase separation structures with both PLLA and PEG blocks in the amorphous state. Amorphous PEGs with high CO _(2) affinity form gas passages that provide excellent CO _(2) /O _(2) permselectivity in such a nanostructure morphology. The gas permeability and permselectivity depend on the molecular weight and content of the PEG and are influenced by the temperature. Copolymers that have a higher molecular weight and content of PEG present better CO _(2) permeability at higher temperatures but provide better CO _(2) /O _(2) permselectivity at lower temperatures. In addition, the hydrophilic PEG segments improve the water vapor permeability of PLLA. Such biodegradable copolymers have great potential for use as fresh product packaging.
展开▼
机译:以二羟基PEG为引发剂,通过L-丙交酯的开环聚合反应合成了可生物降解的聚L-乳酸-聚乙二醇-L-乳酸(PLLA-PEG-PLLA)共聚物。研究了共聚物中不同PEG链段对机械性能和渗透性能的影响。已确定某些添加的PEG会导致PLLA和PEG嵌段均处于无定形状态,从而导致成分依赖性的微相分离结构。具有高CO _(2)亲和力的非晶PEG形成气体通道,在这种纳米结构形态中可提供出色的CO _(2)/ O _(2)渗透性。气体渗透性和渗透选择性取决于PEG的分子量和含量,并受温度影响。具有较高分子量和PEG含量的共聚物在较高温度下表现出更好的CO _(2)渗透性,但在较低温度下提供更好的CO _(2)/ O _(2)选择性。另外,亲水性PEG链段改善了PLLA的水蒸气渗透性。这种可生物降解的共聚物具有用作新鲜产品包装的巨大潜力。
展开▼