【作者】 汪秀丽；

【导师】 王玉忠；

【作者基本信息】 四川大学 ， 材料学， 2003， 博士

【摘要】 聚对二氧环己酮(PPDO)是脂肪族聚酯的一种，具有优异的生物相容性和生物可降解性，被成功应用于制造外科缝合线、骨板和组织修复材料，如螺钉、钩、片和钳等外科器具。PPDO的综合性能相对较好，由于其分子链上含有特有的醚键，使其分子链柔顺性好，聚合物具有优异的柔韧性，抗张强度、打结强度，降解过程中强度保留率大，可制成单丝缝合线。除了在生物体内具有优异的生物相容性和生物降解性以外，在自然界中还存在着多种能使PPDO降解的微生物，这为PPDO更广泛应用于各种环保产品奠定了基础。除了作为医用材料，PPDO还可以用于制造一次性卫生用品如尿布、纸巾等。在能大幅降低合成成本的前提下，PPDO有望广泛应用于制造薄膜、发泡、板材、粘合剂、涂饰剂和无纺布等材料，以满足环保要求。本论文正是为了要进一步扩大PPDO的应用范围，把淀粉这样价格低廉、可再生的天然高分子添加到PPDO中，来降低其成本的同时，提高它的生物降解速率，以满足它作为环境友好材料使用的要求。 由于亲水的淀粉和疏水的PPDO之间缺乏相容性，所以本论文首先采用本体及溶液聚合两种方式合成了淀粉与1，4-对二氧环己-2-酮(PDO)的接枝共聚物(SGP)作为其共混体系的增容剂。由于淀粉分子量庞大、分子链中存在大量的亲水性基团(羟基)以及具有紧密的团粒结构，因此在普通有机溶剂中溶解性能极差。利用淀粉和接枝单体在普通溶剂中进行接枝共聚时就会导致非均相反应，反应性基团接触面小，从而大大地降低了反应活性。所以我们首先对淀粉分子链上的羟基进行改性(三甲基硅烷化处理)，由于三甲基硅基是一个极性很大的基团，它的引入会改变淀粉的溶解特性，使得淀粉在普通有机溶剂中四少l!大学博士学位论文变成可溶。本论文详细地研究了三甲基硅烷化淀粉的合成条件，确定了反应的最佳条件，并对改性淀粉进行了红外和核磁表征。在四氢吠喃溶剂中完成了改性后的淀粉和PDO的接枝共聚反应。 由于溶液聚合涉及到溶剂的处理和回收，过程比较烦琐，所以我们又利用淀粉分子上的轻基和辛酸亚锡一起原位引发PDO的开环聚合，即通过本体聚合方式获得了淀粉伊DO接枝共聚物。用红外光谱、一维及二维核磁共振谱对其微观结构进行了表征，发现可以通过控制反应条件来获得具有不同结构的接枝共聚物。详细地研究了反应温度、反应时间、催化剂用量及PDO单体和淀粉单元的摩尔比对转化率、接枝率和接枝效率的影响。同时发现，当PDO的含量比较低时，体系亲水性较强，有利于在淀粉的CZ和C3上发生接枝反应。随着反应物中PDO含量的增加，体系变得疏水性要强一些，就有利于在淀粉单元的C6上发生反应。随着PDO含量的增加，接枝在淀粉上的PPDO链的数目也增加。接枝链的长度除了起始阶段稍有增加以外，几乎不随着PDO量的增加而增加。也就是说，当PDO与淀粉单元的投料比从4.76增加到7.94时，接枝链的长度却不再增长。这主要是由于随着PDO含量的增加，PDO自聚形成均聚物的可能性也增加了。 采用TG、DSC及热台偏光显微镜等测试手段研究了接枝共聚物热性能、结晶性能、结晶形态和结晶动力学。结果表明，SGP的分解分为两个阶段:第一个阶段在243℃具有最大分解速率，此时是接枝链PPDO的分解;第二个阶段在283℃出现最大分解速率，此时是淀粉开始分解。由于PPDO的加工温度只是略高于其熔点，所以即使SGP在209℃就已开始分解，这也不会影响它在PPDO和淀粉体系中的使用。SGP的热性能与接枝结构有着密切的关系，如果接枝物的接枝链的数目少且接枝链比较短，其结晶能力就差，结晶恰也低。随着接枝链数目的增加及接枝链长度的增长，结晶能力就获得了提高，反映在结晶烩的增长上。从第二次升温曲线上可以容易地观察到5 GP4的玻璃化转变温度为一16℃，比纯PPDO的要低一些，这是由于接枝链的分子量不是太大所造成的。结晶能力随着接枝链的长度和数目的增加而提高;SGP以淀粉为核进行结晶;随着结晶温度的提高，可以观察到球晶特有的黑十字消光图象，呈现放射状球晶;同一温度下，SGP形成的球晶比纯聚对二氧环己酮(PPDO)的晶体小得多;由于不需要成核过程，并且接枝链的分子量不是很大，因此5 GP具有很四川大学博士学位论文高的结晶速率。 本文还对淀粉和PPDO共混体系的热降解行为进行了研究。研究表明，淀粉混入PPDO后，提高了PPDO的热分解温度。加入swt%淀粉后，PPDO的起始分解温度从286℃提高到309℃。含有IOwt%淀粉的PPDO的热性能最好，这可从其起始分解温度得到确认。含有IOwt%淀粉的PPDO的起始分解温度是316℃，在所研究的配比范围内是最高的。进一步提高淀粉的含量并不能使PPDO的热性能获得更大的改善。淀粉地加入改变了PPDO的热降解机理，PPDO的热降解机理从Fl变为D3机理。由于淀粉在290℃以前是稳定的(除了在100℃时有水分释放出)，并没有分解释放出其他物质，这说明淀粉的加入将不会改变PPDO的可回收性。 本论文详细地研究了淀粉的加入对PPDO的热性能的影响，发现添加swt%的淀粉时，淀粉起到成核剂的作用。具体表现在P更多还原

【Abstract】 Poly(1,4-dioxan-2-one) or poly (p-dioxanone), PPDO, is a well-known aliphatic polyester having good physical properties and bio-compatibility, and has been used to make monofilament sutures with good tenacity and knotting. Because the raw material that is used to produce PPDO, p-dioxanone (PDO), which can be obtained by a simple production process from diethylene glycol using some efficient catalysts, becomes inexpensive and available at present, PPDO is viewed as a candidate not only for medical use, but also for universal uses such as films, molded products, laminates, foams, non-woven materials, adhesives, and coatings.In order to lower its cost and expand its application, low-cost natural polymers such as starch can be blended with PPDO. However, the poor compatibility of PPDO with.starch made the blends behave unsatisfied performances. In order to improve their interfacial adhesion, a compatibilizer must be used in the blends. This motivated us to synthesize a novel compatibilizer, starch-g-PPDO, which is also biodegradable and can be used in starch/PPDO blends.Starch-g-poly(l,4-dioxan-2-one) (SGP) was synthesized by using the ring-opening graft polymerization of PDO monomer onto starch backbone via melting and solution, respectively. Due to poor solubility of starch in most organic solvents it is difficult to obtain graft copolymer in solution. So the trimethylsily-protected starch was produced by the reaction of starch and chlorotrimethylsilane in the presence of pyridine. PPDO can be grafted onto starch unit in tetrahydrofuran in the presence of potassium /err-butoxide (/-BuOK) Thereaction conditions of preparing trimethylsilylated starch have been studied systematically. SGP synthesized in solution was characterized by FT-IR and’H-NMR.Because the recovery and purification of solvents are very tedious in preparing SGP in solution, we synthesized SGP in bulk, in which PDO monomers were grafted on the hydroxyl groups of the starch in the presence of stannous octoate (SnOcti). The detailed analysis on the microstructure of the resulting SGP was conducted by using one- and two-dimensional NMR spectroscopy. Reactivity of graft polymerization has been studied. It was found that at the initial stage the grafting reaction occurs mainly on the €2- and Ca- branches of starch units due to lower PDO content and more hydrophilic medium. With the increase of PDO content, the medium becomes hydrophobic and therefore the grafting reaction occurs on the Ce-branch. When the molar ratio of PDO/starch unit increases from 4.76 to 7.94, the PPDO grafts on the starch cannot be further lengthened. The reason for this is that although the reactivity of PDO with starch is enhanced when the PDO content increases, the homopolymerization of PDO monomer is also promoted.The structures and properties of SGP were investigated by FT-IR, HNMR, HMQC, differential scanning calorimetry (DSC), thermogravimetry analysis (TGA), wide-angle-X-ray diffractometry (WAXD) and hot-stage polarizing optical microscope (PM). It was found that the graft structures of copolymers have great effect on their thermal and crystallization behaviors. Because there were many defect sites in the crystalline phase originated from the short grafted chains of PPDO, the crystal structure of the copolymers was much less perfect than that of PPDO. PM revealed that the spherulitic morphology of the graft copolymers depended on graft structures and crystallization temperatures. From the single polarized micrograph of the graft copolymers, it was observed clearly that the starch segments acted as nucleation sites. Both the PM observation and the DSC investigation indicated that the graft copolymers have a fast crystallization process compared with PPDO, especially at higher crystallization temperatures.The thermal properties, crystallization behaviors, spherulitic morphology,rheological properties, biodegradation and mechanical properties of PPDO/starch blends were investigated. Starch improved the thermal stability of PPDO and PPDO/St更多还原