Preparation And Crystallization Properties Of 4-arm Star-Shaped Polyglycolide

In this paper,pentaerythritol(PTO)with four terminal hydroxyl groups was used as initiator to initiate ring-opening polymerization of monomeric high-purine glycolide(GA)monomer under the catalysis of stannous octoate(Sn(Oct)2).The 4-arm star-shaped polyglycolide of the core was characterized and its molecular structure and polymerization process were characterized and explored.The isothermal and non-isothermal crystallization kinetics of the 4-arm star polyglycolide were systematically studied.The molecular structure of the 4-arm star polyglycolide was characterized by nuclear magnetic resonance(~1H-NMR)and infrared spectroscopy(FTIR).Infrared spectroscopy confirmed that the product has a typical aliphatic polyester structure.The nuclear magnetic characterization shows that the methylene signal peak attributed to the initiator pentaerythritol has a significant chemical shift,indicating that the terminal hydroxyl group of the initiator pentaerythritol successfully initiates the ring-opening polymerization of glycolide.The polymerization temperature is 190°C,the reaction time is 3 h,and the molar ratio of catalyst to initiator terminal hydroxyl group is controlled at 1:100.The 4-arm star polyglycolide has the best reaction rate and apparent morphology.The molecular weight can be controlled by varying the arm length of the star polymer,ie changing the ratio of initiator to monomer.The 4-arm star-shaped PGA of the same molecular weight has a lower melting temperature than the linear PGA,and as the molecular weight decreases,the melting temperature also decreases.In addition,the thermal weight loss test indicates that the star-shaped molecular structure leads to a decrease in the heat resistance of PGA,which is manifested by a decrease in thermal decomposition temperature,indicating that the difference in the structure of polyglycolide has a certain influence on its thermal stability.4-arm star-shaped PGA isothermal crystallization studies found that the same crystallization temperature,the higher the molecular weight of the 4-arm star-shaped PGA,the faster the crystallization rate.It is indicated that the effect of highly active chain end groups on the movement of molecular chains plays a dominant role in the star-shaped PGA crystallization process.The Avrami index of linear PGA and 4-arm star PGA is mostly between 2.50 and 2.97,indicating that their nucleation methods are heterogeneous nucleation,and the crystal growth mode is three-dimensional spherulites,indicating that the molecular chain structure changes have not changed.Its nucleation method.The 4-arm star PGA with a large molecular weight polarized microscope(POM)has a larger nucleation density.Under the same crystallization conditions,the low molecular weight 4-arm star PGA crystal is larger in size.The non-isothermal crystallization kinetics of 4-arm star-shaped PGA was studied by Jeziorny method,Owaza method and Mo Zhishen(mo method).The Owaza method is not suitable for the analysis of non-isothermal crystallization kinetics of 4-arm star-shaped polyglycolide.The Jeziorny method found that the non-isothermal crystallization rate constant Z_c of the 4-armed star PGA increased with the increase of the cooling rate,and the semi-crystallization time of the polymer also shortened.Constantly accelerating.The linear value of the linear PGA obtained by Mo Zhishen(mo method)is not much different from that of the 4-armed star PGA,indicating that the introduction of the pentaerythritol core did not change the crystallization mechanism of PGA.