含光可逆C-C键自修复聚氨酯的制备和性能

Preparation and Characterization of Self-Healing Polyurethane Containing Photoreversible C-C Bond

为实现聚氨酯的光诱导自修复,采用4,4-二羟基二苯甲酮(DHBP)和2-溴乙醇为主要原料,经过Williamson醚化等多步反应,合成一种末端带4个醇羟基的四苯基芳香片呐醇单体(THETPED);然后,以其为交联剂,通过与异佛尔酮二异氰酸酯(IPDI)和聚乙二醇(PEG)的加成聚合反应,制备了含光可逆C-C键的聚氨酯薄膜。采用傅里叶变换红外光谱(FT-IR)、核磁共振波谱(NMR)和紫外可见光谱(UV-Vis)等对单体结构进行表征,并借助电子顺磁共振波谱(ESR)研究C-C键的动态可逆性,聚合物则采用FT-IR、热失重(TGA)和差热扫描量热法(DSC)等分析其结构和引入片呐醇单元的影响。结果表明,合成得到了具有预期结构的功能单体和动态共价聚合物,并且C-C键在紫外光照下可以实现动态可逆均裂反应,聚合物链段的室温运动性良好,并且片呐醇单元基本不影响聚合物的热稳定性。采用裂纹修复的方式表征自修复性能,聚合物在紫外光照下(365 nm,5 min)可以完全修复20μm宽的裂纹,而对比样在相同条件下基本无法修复。

To achieve photo-induced self-healing of polyurethane,an aromatic pinacol monomer(THETPED)with four terminal hydroxyl moieties was designed and synthesized through multi-step organic reactions using 4,4′-dihydroxybenzophenone(DHBP)and 2-bromoethanol as raw material.Then,the polyurethane with photo-reversible C-C bonds were prepared through addition polymerization of isophorone diisocyanate(IPDI),polyethylene glycol(PEG)and THETPED.The chemical structure of the pinacol monomer was confirmed by FT-IR,NMR and UV-Vis spectroscopy,respectively.The dynamic reversibility of the included C-C bond in the presence of UV light was studied by electron spin resonance(ESR).Meanwhile,the structure of the polyurethane was examined by FT-IR,thermogravimetric analysis(TGA)and differential scanning calorimetry(DSC).The results show that the polymer with the expected structure was obtained,and the dynamic reversible homolysis reaction of C-C can be triggered under UV irradiation.As revealed by TGA,the pinacol units within the molecule chains don′t affect the thermal stability of the as-synthesized polyurethane.Besides,the resultant polymer exhibits good segmental mobility at room temperature,which is in favor of crack healing.As a result,the polymer with photo-reversible C-C bond can completely repair a 20μm wide scratch under 365 nm UV light within 5 min,while the reference sample shows no visible healing effect under the same conditions.