基于传统化学键/动态硼酸酯键构建的超支化柠檬酸聚酯体系的研究及其应用初步探索

Study on hyperbranched citric acid polyester systems based on traditional chemical bonds/dynamic boronic ester bonds and preliminary exploration of their application

以生物质材料柠檬酸和丙三醇为原料,通过控制反应条件合成了两种不同分子量的端基为羟基的超支化柠檬酸聚酯(HBPE),采用FT-IR、1H-NMR和GPC对HBPE的分子结构、支化度以及分子量进行了表征,其支化度为85%,分子量分别为4115和6011g/mol。再以上述两种HBPE为原料进一步制备了两种不同化学键交联的水溶性聚酯:与丁二酸以传统化学键交联得到的HBPE-SA和与硼砂以动态硼酸酯键交联的络合物HBPE-borax。流变学实验表明,HBPE-borax的力学强度和黏度受含水量和HBPE分子量影响,整体而言,HBPE-borax和HBPE-SA表现为黏度很大的液体,其黏度在剪切速率为30s-1时仍保持在3200Pa·s左右。由于HBPE-borax中含有动态硼酸酯键,赋予HBPE-borax自愈性和pH响应性。吸湿性实验表明两种聚酯在相对湿度为68%的条件下20min即可恢复黏性,基于上述特性初步表明可用作水溶性生物质“不干胶”,并初步探索了黏接性能。

In this research,two biomass materials,citric acid and glycerol,were used as raw materials to synthesize two hyperbranched citric acid polyesters(HBPE)with different molecular weights and hydroxyl end groups by adjusting the reaction conditions.The chemical structure,degree of branching and molecular weights of HBPE were characterized by FT-IR,1H-NMR and GPC.The degree of branching was 85%,while the molecular weights were 4115 and 6011g·mol-1,respectively.Then two HBPEs were further taken to prepare two different chemical cross-linking water-soluble polyesters:HBPE-SA,which was cross-linked with succinic acid through traditional chemical bonds,and HBPE-borax,which was cross-linked with borax through dynamic boronic ester bonds.Rheological experiments showed that the mechanical strength and viscosity of HBPE-borax were affected by the water content and the molecular weights of HBPE.Overall,HBPE-borax and HBPE-SA behaved as very viscous liquids,and their viscosity remained around 3200Pa·s at a shear rate of 30s-1.Since HBPE-borax had dynamic borate bonds,it had self-healing and pH-response properties.The hygroscopicity test indicated that the two polyesters could recover their viscosity in 20minutes under the condition of relative humidity of 68%.Based on all characteristics described above,both HBPE-borax and HBPE-SA could be applied as water-soluble biomass“sticker”,and their adhesive properties were preliminarily explored.