载药互穿聚合物网络体系在竹材中的原位构建及其防霉防裂机理研究

Due to the unique advantages in both resources and qualities, bamboo has become the perfect "Low carbon and environmentally friendly" material that can relive the contradiction of wood supply and demand. However, bamboo is prone to mildew and crack, which inhibits the upgrades of product and the expansion of application fields. In this project, new finds in polymer science will be used to solve bamboo mold and crack. To do this, drug-loaded interpenetrating polymer networks (IPN) will be in situ established in bamboo through simultaneous polymerization and crosslinking. The mutual penetrating and entangling structure in IPN can restrain the cracks resulted from moisture fluctuation, while the drug loaded in IPN can be controlled release, which is a good method to reduce the leachability and degradation of active ingredients, also a novel way to improve the efficacy of mold-resistant chemicals. Chitosan and its derivatives produced from the shells of shrimp and crab can not only tightly bind with bamboo components through amino group and hydrogen group, but also self-crosslink or crosslink during the polymerization of alkenes, thus forming a three-dimensional network. Based on the above considerations, chitosan, chitosan derivatives and functional monomer will be chosen as the main raw materials to in situ establish drug-loaded IPN in the bamboo structure. To elucidate the relationships and effects among IPN, drug and bamboo, the mechanisms for mold and crack resistances will be explored. This project will bring new ideas and reliable theories in solving bamboo mold and crack problems.

竹材以其独特的资源和性能优势成为缓解木材供需矛盾的最佳"低碳环保"材料。但是，霉变和开裂成为制约竹产品升级和应用领域拓展的主要瓶颈。本项目拟借鉴高分子领域的最新成果，在竹材中原位构建相互贯穿、相互缠结的聚合物交联网络，并在网络体系形成过程中同步负载防霉药剂，得到竹材载药互穿聚合物网络复合体系。该体系通过纵横交织的网络体系改善竹材的易裂性，并通过药剂缓释和控释降低防霉剂的流失和降解，提高竹材的防霉性。 源于虾蟹壳的壳聚糖及其衍生物不仅能借助氨基和羟基与竹材牢固结合，还能自交联或在烯烃化合物聚合过程中交联，形成三维立体网络体系。因此，本项目将以壳聚糖、壳聚糖衍生物及功能单体为主要原料，在竹材中原位构建贯穿于细胞腔和细胞壁的载药互穿聚合物网络。在掌握影响该体系构建的基本规律和载药特性的基础上，进一步探索其防霉防裂机理，为同时攻克竹材霉变和开裂两大技术难题提供可靠的理论依据。

竹材的霉、腐和开裂严重制约了竹产品升级和应用拓展。大量研报道关注防霉，同时解决以上抗菌防裂问题的研究较少，通过一步法将抗菌和防裂药剂同时构建于竹材中尚未见报道。项目借鉴高分子领域的研究成果，结合竹材处理要求一步法、水基和原料环保易得等特点，合成并筛选出四种互穿聚合物。将这些聚合物载药并原位构建于竹材中，抑制竹材的防霉、腐和开裂，通过详细表征，分析抗菌和防裂机理。主要结果如下：.竹材中的构建载药壳聚糖/聚乙烯醇（CTS/PVA）、壳聚糖/甲基丙烯酸羟乙酯（CTS/PHEMA）、聚甲基丙烯酸甲酯/聚乙二醇（PAA/PEG）或聚甲基丙烯酸甲酯/甲基丙烯酸羟乙酯（PMMA/PHEMA），能同时提高竹材的尺寸稳定性和抗菌性。四种聚合物处理材在三次浸水-干燥循环中抗胀率最高分别为47.8%、59.0%、72.4%和28.3%；吸湿-干燥循环中抗胀率最高分别为63.1%、86.8%、47.2%和64.6%。载药聚合物处理材抗菌性能高于保护剂单独处理材。竹材中原位构建载有0.2%IPBC的CTS/PVA或PAA/PEG聚合物，处理材的防霉性能比IPBC单独处理材分别提高了7-25%和33-45%。竹材中原位构建CTS/PHEMA或PMMA/PHEMA聚合物体系，处理材在室内防霉测试中均未感染霉菌，防霉效力为100%。防腐试验显示，载有丙环唑的CTS/PVA或PMMA/PHEMA处理材与丙环唑单独处理效果相当，均达到强耐腐等级；载有0.5%PT防腐剂（丙环唑/戊唑醇=3:4）的PAA/PEG处理材防腐效果较PT处理效果差，处理材仅达到耐腐等级；载有丙环唑的CS/PHEMA处理材对白腐菌彩绒革盖菌和褐腐菌密粘褶菌的耐腐性能分别提高了20.2%和69.1%，说明竹材中原位构建CS/PHEMA载药聚合物能大幅度提高竹材的抗菌性。借助扫描电镜、透射电镜和动态力学分析仪等研究抗菌防裂机理，认为载药聚合物不仅能释放药剂达到抑菌的效果，还能借助其在竹材中形成的聚合物网络堵塞细胞壁上的纹孔，减少水分的渗透和水分活度，从而抑制真菌的生长和繁殖。.项目组将部分研究成果用于原竹和重组竹的抗菌防裂处理，与两个企业合作完成了中试和产业化试验，得到了一些进展。项目的开展为同时攻克竹材霉变和开裂两大技术难题提供可靠的理论依据和重要的方法借鉴。