Functionalizing Polylactic Acid Based On D₄^vi Constructed Block Copolymer

Polylactic acid?poly-L-lactide,PLLA?is as a biodegradable thermoplastic polyester widely researched and utilized,and is the most potential material to replace traditional petroleum-based polymers.PLLA has good mechanical strength and modulus,but it breaks at low strain and exhibits inherent brittleness.At the same time,in addition to biodegradation and compatibility,the lack of functionality of PLLA has also become a bottleneck in its application.Therefore,this paper focuses on the problems of toughening,hydrophilicity and shape memory.Based on tetramethyltetravinylsiloxane(D₄^vi),a novel biocarrying?lactose,LA?and polytetrahydrofuran?PTHF?was synthesized.The polymer is modified by PLLA by a blending method to obtain a material that better satisfies the practical application.The following are the main research contents of this paper:First,a new type of polymer carrying LA was designed and synthesised.The triblock copolymer?LA-g-PCL-PMVS-PCL?carrying lactose side groups was synthesized by D₄^vii ring-opening polymerization to get vinyl polymer?PMVS?with pendant groups,ring-opening polymerization of?-caprolactone and esterification,and the PCL chain length and lactose grafting were changed.The rate adjusts the solubility of the synthesized product in chloroform.The polymer exhibits good film forming ability and flexibility after chain extension.Second,blending LA-g-PCL-PMVS-PCL improves PLLA.Film samples were prepared by solution blending coating method.The blending ratio can affect the state of LA-g-PCL-PMVS-PCL molecular chain in the blend system,which affects the thermal properties,mechanical properties and hydrophilicity of PLLA.The PLLA blend film has a water contact angle of at least 67°,a blending ratio of 10/90 by weight,a break point elongation of 70%,and a tensile strength of 27.5 MPa.Third,the design and synthesis of a new x-type polymer?DAPP?gives the PLLA shape note function.A novel x-type polymer?DAPP?in which allyl glycidyl ether,PTHF and PCL copolymers are branched is synthesized by addition,condensation and ring-opening polymerization with D₄^Vi as the central core.The product was characterized by infrared and1H nuclear magnetic methods.DAPP can be used as a shape switch for triggering PLLA by thermal stimulation.At the same time,toughened PLLA is also achieved.And increased the hydrophilicity of PLLA.It was found that the crystal state of DAPP,the recovery effect of the PLLA shape,and the like were related to the blending ratio.The mixing ratio of50/50 DAPP/PLLA can be restored to the original shape at 55°C,25 s,the water contact angle is 70°,the shape fixing rate?Rf?is 94%and the shape recovery rate?Rr?is 65%,and the elongation at break is The rate is as high as 247.7%.