【作者】 滕新荣；

【导师】 胡学超；

【作者基本信息】 东华大学 ， 材料科学与工程， 2002， 博士

【摘要】 超临界CO₂合成技术已逐渐应用到各种聚合物的合成中。它可作为一种连续相的溶剂，代替有机溶剂的使用，减少了对环境的污染。本文选取了丙烯腈和对苯二甲酸乙二醇酯作为研究的对象，分别探索它们在超临界CO₂条件下的合成情况。主要研究结果如下： 1．以超临界CO₂做溶剂，偶氮二异丁腈AIBN做引发剂，成功地进行了丙烯腈的沉淀聚合反应（下文简称CO₂-PAN），并且反应能得到每批20-40克的聚丙烯腈。此外，对于丙烯腈和丙烯酸甲酯在超临界CO₂下的共聚反应，也做了简单尝试。 2．采用¹³C NMR分析技术对CO₂-PAN的立体化学进行了研究。在五单元序列的基础上，对CN碳峰的¹³C NMR谱用统计方法进行了分析，研究表明CO₂-PAN的链增长过程符合Bernoulli统计模型。 3．CO₂-PAN在立构规整性上完全是无规的。其二单元组等规立构（m）的含量为0.4，三单元组等规立构（mm）的含量为0.153，而四单元组等规立构（mmm）的含量为0.057，它比常规水相沉淀聚合（简称R-PAN）或水相悬浮聚合（简称S-PAN）分别低出22％，43％，59％。尽管由这三种聚合反应合成的聚丙烯腈在立构规整性上都是无规的，但CO₂-PAN等规立构度偏低的原因可能是由于所采用的溶剂的非极性效应所至。由于CO₂是非极性分子，在超临界CO₂中聚合比在水相中聚合更容易促使氰基之间的排斥作用，减少了在增长链上形成内消旋（m）的机率。 利用IR光谱对CO₂-PAN三单元组立体规整性做了分析，并且与¹³C NMR方法做了对比，发现mm含量分别为0.16和0.153，结果是吻合的。 4．以已知相对分子质量及其分布的聚丙烯腈宽分布共聚物为标样，采用GPC法，得到了有效的标定直线。根据标定直线测定了超临界CO₂中合成的聚丙烯腈均东华大学博士论聚物的相对分子质量及分布。并将CPC法测得的各种平均相对分子质量结果与粘度法所测得的粘均相对分子质量做了比较，结果是一致的。测得COZ一PAN的粘均相对分子质量大约在1.5火104一1.0火1护创mol，相对分子质量分布人九从冻大部分约在3，o左右，而常规工业上水相沉淀法合成的能用于纺丝的聚丙烯睛粘均相对分子质量一般在2.0火104一8.0火1049/mol左右，相对分子质量分布左凡从么一般小于2.5。这说明用超临界CO:沉淀法合成的PAN相对分子质量能达到与常规水相沉淀法合成的基本一样，但相对分子质量分布较宽。 5.研究了聚合反应条件，如单体和引发剂浓度、反应时间、超临界COZ压力、反应温度对C姚一PA人的相对分子质量，相对分子质量分布及转化率的影响。结果发现，超临界CO:中丙烯睛的沉淀聚合反应遵循一般的自由基反应规律。此外由一于PAN粒子的沉淀效应使反应中产生了自动加速现象。并且在高压下，由于超临界CO:的溶解性增加，从而能提高生成的聚合物的相对分子质量，并且相对分子质量分布变窄。 6.超临界CO:中合成的聚丙烯睛完全具有加工性能。将所得产物进行纺丝实验得到了具有一定强力的、3dtex左右的单孔纤维。纤维的强力与纤度相近的普通睛纶纤维差不多，但断裂伸长较小。此外用液相色谱法测定出由超临界CO:合成的聚丙烯睛中微量丙烯睛的含量很小，完全能达到工业上要求的纺丝标准。 7.对在超临界CO:下合成聚对苯二甲酸乙二醇酷（PET）做了尝试。认为小分子缩合物乙二醇能被超临界CO:萃取，且超临界CO:能充当增塑剂，使反应在较低温度下进行。更多还原

【Abstract】 Supercritical CO2 has been broadly applied as a solvent to produce industrial polymers, because it provides intense advantages as an environmentally friendly, inexpensive and nonflammable alternative to the aqueous and organic solvents. In this dissertation, polymerizations of acrylonitrile and ethylene terephthalate in supercritical CO2 were investigated respectively. The main conclusions are as follows:(1) Utilizing 2, 2’-azo(bisisobutyronitrile) (AffiN) as the free radical initiator and under the condition of supercritical carbon dioxide, the precipitation polymerization of acrylonitrille (hereafter, referred as CO2-PAN) was successfully carried out in our laboratory. In addition, copolymer of (AN-co-MA) was also tried in supercritical CO2.(2) The meso and racemic sequence distribution of the polymer chain is a direct reflection of the characteristic feature of the polymerization reaction by which polymer is synthesized. In order to analyses CO2-PAN polymerization mechanism through sequence distribution of PAN chain, we evaluated the pentad tacticities of CO2-PAN from the intensities of cyano peaks splitting into ten peaks in 13C NMR spectra, all of which are assigned by Kamide et al, and tried to examine these values by statistical methods. It was found that the sequence distributions of CO2-PAN obey Bernoulli statistics.(3) The triad and pentad tacticties, (i.e. the content of mmmm, mmmr, rmmr, mmrm, mmrr, rmrm, rmrr, mrrm, mrrr, and rrrr(m, meso; r, racemic)), of the CO2-PAN were analyzed byC NMR spectra. It was found that CO2-PAN was completely random in stereoregularity. Compared with the aqueous phase suspension polymerization of AN, using AIBN as initiator, (hereafter, referred as S-PAN) and aqueous phase precipitation polymerization of AN, using redox type initiator, (hereafter, referred as R-PAN), it was found isotacticity of CO2-PAN was lower than those of S-PAN and R-PAN, although the three kinds of PAN were all random in stereoregularity. The (m) content of CO2-PAN was about 0.4, the (mm) content 0.153 and the (mmm) content 0.057, which is lower than those of the S-PAN or R-PAN by aqueous phase radical polymerization methods by 22%, 43%, 59% respectively. The lower isotacticity of CO2-PAN may be due to the non-polar property of CO2. Thepolymerization in supercritical CO2 seems helpful to repulsion between cyano groups, which reduce the chance of meso sequence on the propagation chain. The triad isotacticity (i.e. the content of mm) of CO2-PAN was also determined by IR method using Minagawa’s equation of the quantitative relationship between intensity of IR bands and isotaticity percentage. The calculated result is accordant with the C NMR method used.(4) The effective linear molecular weight calibration curve of polyacrylonitrile was obtained using a copolymer standard with a single broad molecular weight distribution. The molecular weights and molecular weight distributions of PAN obtained from precipitation polymerization of acrylonitrile in supercritical CO2 were quantitated by the calibration curve. The viscosity -average molecular weight has also been determined and the results are accordant with the GPC results. TheMv of CO2-PAN was about 1.5X 104~1X 105g/mol and the MWD of PAN were around 3. It seems that the products obtained from precipitation polymerization in supercritical CO2 have slightly broader molecular weight distributions.(5) By varying the concentration of monomer and initiator, the total reaction time, the CO2 pressure as well as temperature, the effects on the molecular weight and MWD have been respectively studied. The molecular weight distribution became broad as the monomer concentration increased. There was no appreciable effect of initiator concentration on molecular weight distribution when AIBN concentration ranged from 1.0% to 2.5%. Changing the density of the continuous phase by manipulating the CO2 pressure had a dramatic effect on the reaction. The higher density CO2 at higher pressure has the greater solvency for the gro更多还原