聚乙烯醇-g-异氰酸酯-脂肪醇梳状接枝共聚物的合成、 结构及热性能

通过甲苯-2,4-二异氰酸酯(TDI)的连接作用, 利用接枝共聚法将具有储热功能的长链脂肪醇[如十八醇(C₁₈OH)、 十六醇(C₁₆OH)和十四醇(C₁₄OH)]接枝到聚乙烯醇(PVA)主链上, 制备出储热能力不同的聚乙烯醇-g-TDI-脂肪醇[PVA-g-TDI-C(n)]梳状接枝共聚物. 通过傅里叶变换红外光谱(FTIR)、 差示扫描量热分析(DSC)、 热重分析(TGA)和X射线衍射(XRD)等方法研究了PVA-g-TDI-C(n)共聚物的热行为和结晶结构. 结果表明, PVA-g-TDI-C(n)共聚物具有良好的储热能力, 储热能力随侧链碳原子数目和侧链接枝度的增加而增大, 但明显低于长链脂肪醇的储热能力. PVA-g-TDI-C(n)共聚物具有良好的热稳定性, 失重温度在324~330 ℃之间. 从侧链受限运动角度探讨了影响PVA-g-TDI-C(n)共聚物热性能和有序堆砌结构的原因.     

含氟丙烯酸酯聚合物乳胶膜表面性质

采用XPS和界面张力仪分别测定了含氟丙烯酸酯聚合物乳胶膜表面的组成及水在其表面的动态接触角, 并用状态逼近方程模型计算了含氟聚合物乳胶膜的表面张力, 考察了温度对乳胶膜润湿性的影响. 结果表明, 含氟聚合物乳胶膜表层较深处的F 1s信号强度比近表面要弱, 乳胶膜表面张力随表面氟原子浓度增加在一定程度上呈现线性下降；含氟侧链(Rf)较长(碳原子数n＞6)的含氟聚合物, 其表面张力随Rf单元含量增加而下降的趋势显著高于Rf较短(n≤6)的含氟聚合物, 而水在含氟聚合物乳胶膜表面上的后退接触角θr随n增大出现急剧上升, n≥10 时, θr值几乎恒定不再随n增大而改变. 此外, 参与共聚的非氟丙烯酸酯酯基碳链较短时, 水在共聚物乳胶膜表面的θr随氟单元含量增加而增加的趋势更显著；温度超过40 ℃后, 水对聚合物乳胶膜的润湿性随温度上升略有改善.     

含氟两亲接枝共聚物的制备及其结晶行为

采用大分子单体技术合成了一系列以聚乙二醇为支链、甲基丙烯酸六氟丁酯为主链的含氟两亲接枝共聚物(PHFMA-g-PSPEG)。用1HNMR和凝胶色谱(GPC)对制备的大分子单体和两亲接枝共聚物的结构进行了表征。利用示差扫描量热法(DSC)、X射线衍射(XRD)和偏光显微镜(POM)测试技术对含氟两亲接枝共聚物的结晶行为进行了研究。DSC和XRD结果表明,随着共聚物中含氟链段质量分数的增加,其结晶温度(Tc)和结晶度(Xc)均降低,而结晶熔融温度(Tm)先减小后增加。POM发现,随着共聚物中含氟链段质量分数的增加,其结晶速度减慢,共聚物形成清晰球晶的能力减弱,当共聚物中含氟链段质量分数为57%时,含氟两亲接枝共聚物已不能形成清晰的球晶。     

乙烯-α-烯烃共聚物的结晶性能及其临界序列结晶长度的研究

本文用DSC、WAXD及偏光显微镜(PLM)方法,研究了化学反应法催化剂合成的乙烯-α-烯烃共聚物的结晶性能及其临界序列结晶长度。结果表明,随共聚物中α-烯烃含量增大,共聚物的微晶尺寸、结晶度及熔点均逐渐减小,而晶胞参数增大。变化的辐度戊烯>辛烯。共聚物的临界结晶序列长度(n)和k值均戊烯<辛烯。上述结果表明影响支链进入晶格的主要因素是α-烯烃支链长度和结构。     

不同接枝度的十八硫醇化聚氯乙烯梳状聚合物的结构和性能

通过亲核取代反应,制备了一系列不同接枝率的十八硫醇(C_(18)H_(37)SH)接枝改性聚氯乙烯(PVC)(记作PVCS18).通过傅立叶变换红外光谱(FTIR)、核磁共振氢谱(1H-NMR)、示差扫描量热仪(DSC)、热重分析(TG)和X射线衍射(XRD)对PVCS18的结构、相变行为、热稳定性和热能行为进行了研究.结果表明,随十八硫醇钠(C_(18)H_(37)SNa)投料的增加,PVCS18接枝率增加,最高达到50.2%.PVCS18相转变的出现,主要是接枝的十八烷基链段贡献的.随接枝率由8.5%增加到50.2%,相转变温度由61.7℃升高到66.3℃,热焓值由5.3 k J/mol提高到50.9 k J/mol,结晶碳原子数从1.4增加到13.8.主侧链间连接键的极性和基团大小明显影响侧链烷基的结晶能力及可结晶碳原子数目.PVCS18的热稳定性较PVC的没有明显热损失行为出现,该材料可在较高的温度下加工使用.     

烷基化程度对N-十八烷基化聚乙烯亚胺梳状高分子结构的影响

利用烷基化方法制备了烷基化取代程度(DS)介于47%～17.6%的N-十八烷基聚乙烯亚胺(PEI18C)梳状高分子.通过红外光谱、差示扫描量热法(DSC)、X-射线衍射和热失重分析等方法研究了PEI18C梳状高分子的结构、结晶行为和热稳定性,探讨了侧链烷基DS对C18侧链结晶及临界结晶行为的影响.结果发现,随DS的降低,PEI18C梳状高分子的结晶度由54.0%降至20.3%,可结晶碳原子数目由11.4个降到4.3个.受限于PEI骨架上C18烷基侧链的堆积排列模式并没有发生根本变化,仍以六方晶胞的形式进行排列.结果表明,侧链烷基DS或沿主链的侧链烷基分布密度对梳状高分子的结晶行为和临界结晶能力有明显的影响.从侧链结晶的角度,分析了侧链烷基取代度对梳状高分子结晶及热稳定性的影响.     

乙丙共物聚的结晶速率与序列结构

本文用(体)热膨胀计法研究了共聚物组成、催化体系对乙丙共聚物结晶速率的影响。结果表明,同一催化体系乙丙共聚物的最大结晶速率(1/t_((1/2)(max)))随共聚物中乙烯含量的增加而增大。不同催化体系对二元乙丙共聚物的1/t_((1/2)(max))次序为:VOCl_3~->V_(5-9~-)>V_((aca?)3~-)。加入活化剂ETCA的各催化体系的二元乙丙共聚物的1/t_((1/2)(max))为VOCl_3~-ETCA>V_(5-9~-)ETCA>V_((ocac)~-)ETCA。结合结晶度、T_g、以及不同序列分布共聚物组成的测定,可推测VOCl_3~-体系乙丙共聚物具有较长的聚乙烯序列结构,V_(5-9~-)体系次之,V_((acac)_3~-)体系的乙丙共聚物分子链有更多的无规结构。     

苯乙烯-氧乙烯-苯乙烯三嵌段聚合物的受限结晶行为的反气相分析

 采用反气相法研究了苯乙烯 氧乙烯 苯乙烯三嵌段结晶聚合物 (PS PEO PS)的结晶熔融相变 ,测定了PS PEO PS的结晶度、熔点以及熔程 ,探讨了正构烷烃探针分子的碳链长度对测定结果的影响。研究结果表明 :PS PEO PS的微相分离对PEO链段的结晶行为有较大的影响 ,其晶体结构中存在由多种不完善PEO结晶和PS非结晶构成的中间层 ;正构烷烃探针分子的碳链长度对测定PS PEO PS的熔点和熔程无影响 ,但对结晶度测定和PEO结晶熔融相变的检测影响较大 ,所测得PS PEO PS的结晶度随正构烷烃探针分子碳链的增长而降低。     

全对位聚芳醚砜醚酮酮的结晶行为研究

以AlCl3/DCE/DMF为溶剂体系,采用低温溶液缩聚合成全对位聚醚砜醚酮酮(p-PESEKK)树脂,研究了端基、分子量及溶剂体系对树脂的溶剂诱导结晶行为的影响.结果表明,在AlCl3/DCE/DMF的良溶剂中制得的p-PESEKK为低结晶度聚合物,由于分子链中四面体结构砜基的影响,树脂熔融后很难再结晶;随脂肪链端基碳原子数的增加,溶剂诱导结晶速度逐渐下降,结晶度降低,与主链结构相同的端基更有利于结晶的形成;高分子量的p-PESEKK端基的比例相对较小,有利于溶剂诱导结晶.     

丙烯酸酯共聚物无皂水溶胶稳定性的研究

用溶液聚合法合成了四种AA含量不同的丙烯酸酯共聚物(MMA/BA/HEMA/AA)，通过中和AA使共聚物带有—COO~-能起自乳化作用分散于水中而成为无皂水溶胶．TEM观察表明水溶胶粒子呈球状，单分散性好，粒径随AA含量增加而变小，在30～90 nm范围．用电导滴定法测定水溶胶粒子中—COOH和—COO~-的分布，表明绝大部分—COO~-处于粒子表面，并且随AA含量增加，粒子表面的—COO~-增多，Zeta电位增大，这是导致水溶胶的抗电解质稳定性(以C.C.C.值反映)和贮存稳定性(以表现粘度反映)随AA含量增加而提高的主要原因。     

Photoregulated binding ability of azoaromatic polymer for surfactant

Water-soluble polymeric azodyes containing an azobenzene moiety in their side chain, p-phenylazoacrylanilide (PAAn)–acrylamide (AAm) copolymers, were synthesized and the adsorption-desorption behavior of sodium dodecyl sulfate (SDS) onto these copolymers in water was investigated by means of conductivity measurements, with attention to the hydrophobicity of the copolymer. The conductivity of the PAAn-AAm copolymer/SDS complex aqueous solution decreased with increasing PAAn composition in the copolymer. This result indicates that the SDS molecules adsorbed onto the copolymer. The adsorption state of SDS molecules on the copolymer was considered to take a micellelike form. When the hydrophobicity of the PAAn-AAm copolymer was decreased by means of the photoisomerization of an azodye moiety, the conductivity of the PAAn-AAm copolymer/SDS aqueous solution increased. This phenomenon can be explained as a result of desorption of SDS molecules from the copolymer. When the light source was cut off, the conductivity took on its original value. This indicated that SDS was desorbed by the photochemical trans to cis and adsorbed by cis to trans isomerization of the PAAn moiety.     

Construction of lamellar morphology by side-chain crystalline comb-like polymers for gas barrier

A comb-like polymer containing crystallized alkyl side chains and the intermolecular hydrogen bonds between the linking groups was fabricated by grafting long-chain fatty amine onto poly(styrene-co-acrylic acid)_n (P(S-AA)_n, wherein “n” denoted AA feed ratio). The chemical structures and crystallization behaviors of the comb-like polymer P(S-AA)_n-g(p) (wherein “p” denoted the number of side-chain carbon atoms) were analyzed by Fourier transform infrared, gel permeation chromatography, X-ray photoelectron spectroscopy, and X-ray diffractometer, differential scanning calorimetry, atomic force microscopy, respectively. It was found that the lamellar morphology could be generated by controlling the grafting density and side chain length of P(S-AA)_n-g(p). Moreover, it was identified that the hydrogen bonds between amide groups could enhance the crystallinity and then adjust the interlamellar spacing of lamellar phase. As a result, P(S-AA)₇₀-g(18) with the highest degree of crystallinity and closely packed lamellar morphology showed a good gas-barrier performance, and the nitrogen permeability reached 1.78 × 10^?14 cm³·cm/cm²·s·Pa. Furthermore, the permeation switch of the obtained comb-like polymer could reach 500 times traversing the melting point.     

Ethylene copolymers with Fischer-Tropsch olefins

The properties of ethylene copolymers, terpolymers and multipolymers prepared with even and uneven carbon number linear and branched α-olefins were compared. The most likely microstructures of ethylene/linear α-olefin copolymers was assigned by considering co-unit bulkiness, average crystallizable sequence lengths and thermal properties. The higher α-olefins were found to be more effective at decreasing density, but peak melting temperatures were higher. In terpolymers where lower α-olefins such as 1-butene and 1-pentene were used as comonomers, density was decreased more than the mathematical average expected from the ratio of comonomers in the terpolymers. Peak melting temperatures were also lower. Based on NMR evidence and the microstructures of the different copolymers the rationale for this occurrence could be ascribed to decreased clustering for these terpolymers. Branched α-olefins produced ethylene co- and terpolymers with significantly decreased densities as compared to the linear α-olefins. Impact strength of these polymers was also substantially higher, even at low comonomer content. Thermal evidence indicates that the microstructure of the co- and terpolymers containing branched α-olefins are very similar to that of the copolymers prepared with linear α-olefins of the same carbon number.     

Sequence distribution of partially hydrolyzed poly(vinyl acetate)

Copolymers of vinyl acetate and vinyl alcohol were studied by differential thermal analysis. The melting points of the copolymers are not a simple function of the composition, but depend on the method of preparation of the copolymers. Partial saponification of poly(vinyl acetate) with sodium hydroxide leads to high melting, ordered copolymers, while reacetylation of poly(vinyl alcohol) leads to low melting, random copolymers. Catalytic alcoholysis of PVAc yields copolymers intermediate in melting point and order. The results are treated by assuming that equal melting points indicate similar sequence length distributions of crystallizable units.     

Comb-like ionic complexes of cationic surfactants with bacterial poly(gamma-glutamic acid) of racemic composition

Comb-like ionic complexes, nATMA . PG(DL)GA, were prepared from microbial poly(gamma-glutamic acid), with a nearly racemic configuration, and alkyltrimethylammoniun bromides, with linear alkyl chains containing an even number of carbon atoms, n, ranging from 12 to 22. The complexes had a nearly stoichiometric composition, displayed thermal stability up to temperatures above 200 degrees C and were insoluble in water but soluble in organic solvents. In the solid state, they were arranged in a regularly layered structure with the alkyl side chain crystallized for n > or = 18. Heating above melting entailed a contraction in the interlayer distance which varied from 1 to 10% depending on the value of n. Comparison with data reported on similar complexes obtained from nearly enantiomerically pure poly(gamma-glutamic acid) revealed an overall behavior very similar for the two series but with specific significant differences concerning side chain crystallinity and dimensional response to temperature.     

含硝基偶氮苯侧基的丙烯酸酯液晶聚合物的合成、结构与性质研究(Ⅲ)——分子结构对结晶的影响

以含硝基偶氮苯侧基的丙烯酸酯液晶聚合物为研究对象,利用DSC、WAXD、偏光显微镜等手段研究了分子结构对侧链液晶聚合物结晶行为的影响.结果表明:丙烯酸酯类液晶聚合物的晶区是由介晶基团的规整排列形成的,大分子主链和柔性间隔基不参与结晶.随着柔性间隔基长度的增加,晶区分子排列有序性提高,结晶度增大;非晶共聚组分MA含量的增加,限制了介晶基团的有序排列,当MA含量超过83％后,只得到非晶共聚物.     

Structure of crystalline polymers with unbranched long side chains

The structure and thermodynamic properties of atactic and isotactic acrylic and methacrylic polymers containing 16–18 carbon atoms in the n-aliphatic side chains, and of copolymers of hexadecyl acrylate with isopropyl acrylate were studied by means of x-ray and differential thermal analysis. The crystallization of branched acrylic and methacrylic polymers and of acrylic copolymers proceeds in the form of a hexagonal crystal, regardless of the configuration of the backbone chain. Methods of ordering branched macromolecules are proposed, and the melting points, heats and entropies of fusion determined. The role of flexibility of the backbone chains in ordering and the crystallization processes was determined. In the case of poly(n-alkyl acrylates) the backbone chain is involved in the crystalline lattice; this is not the case in methacrylates and copolymers of hexadecyl acrylate with isopropyl acrylate. Some similarity was assumed between the structure of biopolymers and synthetic branched polymers.     

Preparation of 6-O-(4-alkoxytrityl)celluloses and their properties

Cellulose was reacted with a series of 4-alkoxytrityl chlorides (C(n)TCl, n: number of carbon atoms in a saturated alkyl chain) under homogeneous reaction conditions in LiCl-N,N-dimethyl acetoamide to give a series of 6-O-(4-alkoxytrityl)celluloses (C(n)TC) with a high degree of substitution (DS), from 0.94 to 0.99, and with high regioselectivity at the 6-O position. Solubility of the C(n)TC in nonpolar solvents depended on the alkyl chain length: as the alkyl chain lengthens, cellulose derivatives become more hydrophobic and are readily soluble in nonpolar solvents, but not in polar solvents. Acetates of the C(4)-C(18)TC (C(4)-C(18)TCAc) showed anisotropic structures over melting temperatures (T(m)) examined under a polarized optical microscope (POM). Over isotropization temperatures (T(i)), flow birefringence were detected for C(12)-C(18)TCAc. The T(m) and T(i) decreased linearly with an increasing number of carbon atoms in the alkyl substituent. Wide-angle X-ray scattering (WAXS) studies of C(n)TC indicated that the fully extended side chains were perpendicular to the polymer backbone and interdigitated. These C(n)TC with the improved solubility may be used as starting materials for further derivatization focused on the secondary hydroxyl groups at the C-2 and C-3 positions.     

Side‐chain crystallization behavior of graft copolymers consisting of amorphous main chain and crystalline side chains: Poly(methyl methacrylate)‐graft‐poly(ethylene glycol) and poly(methyl acrylate)‐graft‐poly(ethylene glycol)

Graft copolymers consisting of amorphous main chain, poly(methyl methacrylate) (PMMA), or poly(methyl acrylate) (PMAc), and crystalline side chains, poly(ethylene glycol) (PEG), have been prepared by copolymerization of PEG macromonomers with methyl methacrylate or methyl acrylate (MMAx or MACx, respectively). Because of the compatibility of PMMA/PEG and PMAc/PEG, from small‐angle X‐ray scattering results, the main and side chains in graft copolymers were suggested to be homogeneous in the molten state. Differential scanning calorimetry (DSC) cooling scans revealed that PEG side chains for graft copolymers with large PEG fractions were crystallized when the sample was cooled, with a cooling rate of 10 °C/min. The spherulite pattern observed by a polarized optical microscope suggested the growth of PEG crystalline lamellae. Crystallization of PEG in MMAx was more restrained than in MACx. From these results, we have concluded that the crystallization behavior of the grafted side chains is strongly influenced by the glass transition of a homogeneously molten sample as well as dilution of the crystallizable chains. Domain spacings for isothermally crystallized graft copolymers were described by interdigitating chain packing in crystalline–amorphous lamellar structure. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 79–86, 2005