【作者】 王炳涛；

【导师】 方征平；

【作者基本信息】 浙江大学 ， 高分子化学与物理， 2010， 博士

【摘要】 20世纪合成高分子材料的问世及其快速发展极大地改善了人类生活,但同时大量塑料废弃物也造成了严重的环境污染。近年来随着人类环保意识的增强,可降解高分子材料的研究与开发越来越引起人们的高度重视。脂肪族聚酯由于具有良好的生物降解性能已成为可降解高分子材料领域研发的热点,然而较差的热稳定性和力学性能以及较高的生产成本制约了其进一步发展。芳香族聚酯虽不具备生物降解性能,却具有优异的热稳定性和力学性能。因此,结合脂肪族聚酯和芳香族聚酯各自优点,设计、合成新型可降解脂肪族-芳香族共聚酯材料已成为人们关注重点。在此背景下,本论文主要开展了两大部分的研究工作：第一部分为可降解脂肪族-芳香族共聚酯的合成及性能研究；第二部分则采用纳米粒子杂化的方法对可降解脂肪族-芳香族共聚酯进行改性。在第一部分工作中,首先以对苯二甲酸(TPA)、1,4-丁二醇(BDO)和乳酸低聚体(OLLA)为原料,采用经济性和环保性更佳的直接酯化熔融缩聚法合成了一系列具有不同组成配比的可降解脂肪族-芳香族共聚酯(PBTL)。通过NMR、FT-IR、DSC、TG、XRD、DMA等手段对其结构与性能进行了表征,研究发现共聚酯的玻璃化转变温度、热稳定性以及力学性能随着共聚酯中脂肪族乳酸组分含量的减少而逐步增加。共聚酯的降解实验表明,乳酸链段的引入赋予共聚酯良好的降解性能,且该材料的降解性能可通过调节共聚酯中乳酸的含量而方便地调控。其次,为了进一步提高可降解共聚酯的热稳定性和力学性能,在TPA、BDO和OLLA共聚反应基础上添加共聚组分刚性二元醇环已烷二甲醇(CHDM),通过直接熔融缩聚反应合成了一系列具有不同CHDM含量的可降解脂肪族-芳香族共聚酯(PBCTL),并对其结构与性能进行了表征。研究发现CHDM的反应活性比BDO高,当CHDM含量为5 mo1%时,产物的重均分子量高达89400 g/mol。CHDM刚性环结构的引引入能有效地提高共聚酯的热性能和力学性能,当CHDM含量由0 mmo1%增加至5 mo1%时,共聚酯的玻璃化转变温度、初始分解温度以及拉伸强度分别由26.9℃,282.5℃和6.4 MPa大幅提升至36.2℃,309.7℃和19 MPa。第三,为了进一步改善共聚酯的降解性能,在TPA、BDO和OLLA共聚反应基础上加入亲水性二元醇聚乙二醇(PEG),采用熔融缩聚反应合成了一系列具有不同PEG分子量和含量的可降解脂肪族-芳香族共聚酯(PBTLG),并对其结构与性能进行了表征。研究发现柔性PEG的加入降低了反应体系粘度,促进了缩聚反应充分进行,最终得到重均分子量高达177000 g/mol的可降解共聚酯材料。吸水率和水接触角测试表明PEG亲水链段的引引入极大地改善了共聚酯的亲水性,进而显著地提高了共聚酯的降解性能,其中PBTLG1000-1.0在60℃的PBS溶液中降解40天质量损失达39%。在第二部分工作中,首先采用Si02作为纳米粒子源,在TPA、BDO和OLLA共聚反应基础上,通过原位熔融缩聚反应将Si02纳米粒子引入到聚合物中制备得到一类含Si02粒子的可降解脂肪族-芳香族共聚酯纳米复合材料,并对其结构与性能以及粒子形貌进行了表征。研究发现在缩聚反应过程中,Si02粒子表面的硅羟基与反应生成的共聚酯发生原位缩合反应,使Si02粒子表面接枝上共聚酯分子链。Si02粒子表面的聚合物链不仅有效地阻碍纳米粒子自身的团聚使其均匀分散,同时增强Si02无机相与共聚酯基体有机相的界面粘合力,大幅提高了复合材料的热稳定性和力学性能。水降解实验表明,Si02粒子的存在未对复合材料的降解性能产生显著影响。其次,从分子设计出发,以氨基POSS化合物(AI-POSS)和羟乙基丙烯酸酯(HEA)为原料,采用Michael加成反应合成了一种新型双官能团POSS化合物(BH-POSS),并在TPA、BDO和OLLA共聚反应基础上,通过原位共缩聚将BH-POSS和另外两种POSS化合物(AI-POSS与PEG-POSS)引引入到聚合物中制备得到一类含POSS笼形结构的可降解脂肪族-芳香族共聚酯纳米杂化复合材料,同时对其结构与性能以及POSS粒子分散状况进行了表征。研究发现AI-POSS物理分散在复合材料基体中但发生明显的纳米粒子团聚现象,而BH-POSS能通过化学共聚反应将其纳米笼形结构以共价键链接在共聚酯分子主链上,这有效地避免POSS粒子的团聚,使之达到均匀分散,因而复合材料的热稳定性和力学性能均显著提高。水降解实验表明,含有多个亲水性基团的PEG-POSS的引入在一定程度上改善了复合材料的降解性能。更多还原

【Abstract】 During the 20th century the advent and rapid development of synthetic polymer materials greatly improved the level of human’s life, but a huge number of plastic waste also caused serious environmental pollution. In the recent years, people have payed more and more attention to investigating and developing novel biodegradable polymers as their consciousness of environmental protection improved. Due to their good biodegradability, aliphatic polyesters have been regarded as one of the most important biodegradable polymers and became a hot research topic. However, the poor thermal stability and mechanical properties as well as relative high cost have drastically restricted their application. On the contrary, aromatic polyesters have excellent thermal stability, good mechanical properties and relative low cost, although they could not be degraded. Therefore, incorporation of biodegradable aliphatic units into the molecular chain of aromatic polyesters has been regarded as an effective strategy to obtain novel biodegradable copolyesters. In this dissertation, two main research have been carried out. First, synthesis, characterization and properties of degradable aliphatic aromatic copolyesters; second, modification of degradable aliphatic aromatic copolyesters by nanohybrids or nanocomposites.In the first part, degradable aliphatic-aromatic copolyesters, poly(butylene terephthalate-co-lactate) (PBTL) were synthesized via environment-friendly and economical direct melt polycondensation of terephthalic acid (TPA),1,4-butanediol (BDO) and poly(L-lactic acid) oligomer (OLLA). NMR, FT-IR, DSC, XRD and DMA analysis clearly indicated that the glass-transition temperature, thermal stability and tensile strength were gradually increased with the decrease of aliphatic lactate moieties in the final copolyesters. Hydrolytic and soil degradation results demonstrated that the incorporation of lactate moieties into aromatic polyesters endowed the copolyesters good degradability and their degradation behaviours could be easily tailored through adjusting the lactate molar content in the copolyesters. In order to enhance the thermal stability and mechanical properties, one copolymerized component, rigid diols cyclohexanedimethanol (CHDM) was added in the TPA, BDO and OLLA reactions to synthesize a series of degradable aliphatic-aromatic copolyester (PBCTL). The results demonstrated that CHDM had higher reactivity than BDO. When the content of CHDM was 5 mol%, the weight-average molecular weight of the copolyester was up to 89400 g/mol. The incorporation of CHDM rigid ring structure dramastically improved the thermal stability and mechanical properties of the copolyesters. When the CHDM content increased from 0 mol% to 5 mol%, the glass-transition temperature, initial decomposition temperature and tensile strength were significantly increased from 26.9 0 C,282.5℃and 6.4 MPa to 36.2℃,309.7℃and 19 MPa.To further improve the degradability, one hydrophilic diol, polyethylene glycol (PEG) was selected as copolymerized componet to react with TPA, BDO and OLLA via direct melt polycondensation, and synthesized a series of degradable aliphatic-aromatic copolyester (PBTLG) with different PEG molecular weight and content. The results indicated that adding PEG decreased the viscosity of reaction system, promoted the condensation reaction and finally obtained copolyester with the weight-average molecular weight up to 177000 g/mol. Water absorption and water contact angle measurements showed that the introduction of hydrophilic PEG remarkably improved the hydrophilicity and significantly increased the degradation rate of the polyesters. For example, the weight loss of PBTLG1000-1.0 was up to 39% after 40 days at 60℃in PBS.In the second part, nano-SiO2 was first selected as one nanoparticle to copolymerize with TPA, BDO and OLLA via in situ melt polycondensation and prepare a novel degradable aliphatic-aromatic copolyester nanocomposites. The results revealed that during the polycondensation, the abundant hydroxyl groups on the surface of nano-SiO2 provided potential sites for in situ grafting with the simultaneous resulted copolyester, so that the SiO2 nanoparticles were chemically wrapped with copolyester main-chains. The copolymer chains grafted onto SiO2 particle surface not only effectively impeded nanoparticles aggregated and made good disperse, but also enhanced the interfacial adhesion between SiO2 inorganic phase with the organic phase copolyester matrix. So the thermal stability and mechanical properties of the PBTL/SiO2 nanocomposites substantially increased. Hydrolytic degradation indicated that the degradability of the composites did not be obviously affected due to the introduction of SiO2.Secondly, a new POSS nanocompound containing two functional groups, BH-POSS, was synthesized via Michael addition reaction of amino POSS compounds (AI-POSS) with hydroxyethyl acrylate (HEA). Based on the polycondensation of TPA, BDO and OLLA, BH-POSS and two other POSS compounds (AI-POSS and PEG-POSS) were introduced into the resulting copolyesters and prepared a novel kind of degradable aliphatic-aromatic copolyester nanohybrids containing POSS. The results suggested that AI-POSS just dispersed physically and aggregated seriously in the composites, but BH-POSS could take part in the copolymerization to make their nanocage structure covalently linked to the main-chains of copolyesters, which effectively prevented the agglomeration of POSS nanoparticles and made POSS dispersed uniformly in the matrix, thus the thermal stability and mechanical properties of the nanohybrids were significantly enhanced. Hydrolytic degradation showed that the incorporation of PEG-POSS containing hydrophilic groups improved the degradability of the nanocomposits to some extent.更多还原