扩链剂对水性聚氨酯乳液的影响

通过自乳化聚合引入低分子扩链剂制得具有嵌段结构的阴离子型水性聚氨酯乳液。研究了不同扩链剂及其用量对聚醚型和聚酯型聚氨酯乳液的影响。结果表明,以乙二醇为扩链剂制得的聚氨酯乳液稳定性较好,且所得的聚酯型聚氨酯涂膜的力学性能也较好,但耐水性较差。扩链剂的最佳用量为2.05%(质量分数)左右。     

扩链剂对UV固化聚氨酯性能的影响

以聚己二酸一缩二乙二醇酯-2000为软段,不同二元醇扩链剂和异佛尔酮二异氰酸酯(IPDI)为硬段,丙烯酸羟乙酯(HEA)封端,采用预聚体法合成UV固化聚氨酯.分析了不同二元醇扩链剂的相对动力学活性;通过红外光谱表征了光固化聚氨酯树脂的结构,研究了不同的二元醇扩链剂对光固化膜力学性能、耐热性能和使用性能的影响.结果表明,反应温度80℃,乙二醇(EG)与苯基异氰酸酯(PI)的反应速率最快,1,2-丙二醇(1,2-PEG)与PI的反应速率最慢;以1,4-环己烷二甲醇(CHDM)为扩链剂的聚氨酯膜力学性能和耐热性最好.     

聚氨酯组成与结构对透明性和力学性能的影响

聚氨酯软硬链段之间的结晶分相行为严重影响材料的透明性和力学性能。使用二环已基甲烷二异氰酸酯、环氧丙烷聚醚和1,3-丁二醇扩链剂合成的软质透明聚氨酯呈无定形结构,当硬段含量为47%(wt)时,样品具有较好的透明性和力学性能。此时透光率93%,抗张强度18MPa、伸长率358%、邵氏硬度90。样品在放置过程中无变黄现象。     

交联型聚氨酯阻尼材料性能研究

采用两步法合成了一系列聚醚型聚氨酯,其中异氰酸酯和聚醚多元醇当量比为1.6～2.3.利用动态热机械分析仪(Dynamic Thermomechanical Analysis,DMA)测试其动态力学性能,研究了异氰酸酯官能度、聚醚多元醇官能度以及扩链剂官能度对聚氨酯材料阻尼性能的影响.结果表明,引入多官能度异氰酸酯能改变聚氨酯材料的tA(tanδArea),多官能度异氰酸酯(PAPI)取代双官能度异氰酸酯(TDI),T_g处损耗因子存在最高值,且tA随PAPI取代越多逐步降低.增加PAPI和扩链剂1,4-丁二醇,T_g处损耗因子整体呈下降趋势,tA存在最大值,且损耗因子最高为1.36(10 Hz).提高聚醚多元醇的平均官能度可以有效改善聚氨酯材料的阻尼性能,M_n=3000D的聚氧化丙烯三醇(GP330)和M_n=2000D的聚氧化丙烯二醇(PPG2000)摩尔比为1:1时,损耗因子(T=T_g)最高;添加丙三醇会降低材料损耗因子(T=T_g).损耗模量随GP330增加而增加,随丙三醇增加而增加(TT_g).     

双螺杆反应器法制备高相对分子质量聚乳酸共聚物的研究

采用熔融缩聚法合成一定相对分子质量的聚乳酸（PLA），然后通过双螺杆反应挤出机与聚已内酯多元醇（PCL）的聚氨酯预聚体进行熔体扩链，制备聚乳酸共聚物。研究了熔体扩链产物的相对分子质量、形态结构、热性能和力学性能。结果表明，双螺杆反应挤出制备聚乳酸共聚物是可行的，熔体扩链后产物的相对分子质量有大幅度提高，产物是热塑性的，并且比釜式反应混合效果好。     

改性HTBN型聚氨酯弹性体的配方优化研究

以端羟基聚丁二烯—丙烯腈共聚物(HTBN)为软段、聚醚(酯)多元醇为改性剂,采用浇铸工艺制备聚氨酯弹性体(PUE)。研究了聚醚(酯)多元醇种类、分子量以及用量对PUE力学性能的影响,研究了二异氰酸酯、扩链剂种类对PUE力学性能的影响。实验结果表明:以HTBN与PTMG-1000混合物(质量比为1 1)为软段、PPDI为硬段、E-300作为扩链剂制备PUE,当预聚体NCO%为6.0%、NCO/NH2摩尔比为1.05,预聚体浇注固化后在115℃热处理2 h,得到的PUE力学性能最佳。PUE的拉伸强度为48.23 MPa、撕裂强度为165.26 N/mm、断裂伸长率为652.45%、硬度(邵氏A)为97。     

HTPB/TDI/MCDEA型聚氨酯弹性体的研制

以端羟基聚丁二烯(HTPB)、甲苯二异氰酸酯(TDI)为主要原料合成预聚体,以4,4’-亚甲基双(3-氯-2,6-二乙基苯胺)为扩链剂,通过浇铸成型制备聚氨酯弹性体。实验采用电子万能试验机和邵氏A硬度计对聚氨酯弹性体的力学性能进行了测试,结果表明:当预聚体NCO含量为4.13%、NH2/NCO摩尔比为0.90时,聚氨酯弹性体的综合力学性能最佳;后硫化时间、环境湿度对聚氨酯弹性体的力学性能均有一定影响,使用新型扩链剂4,4’-亚甲基双(3-氯-2,6-二乙基苯胺)制得的聚氨酯弹性体的力学性能普遍好于扩链剂MOCA。     

含醚键二胺类为扩链剂的嵌段聚醚氨酯的合成及其性能研究

用腈乙基化反应由丁二醇和一缩二乙二醇制备了含醚二腈,经兰尼镍加压氢化合成了相应的含醚二胺,将此类二胺作为扩链剂分别与聚四次甲基醚二醇和4,4′-二苯基甲烷二异氰酸酯的预聚物反应得到相应的嵌段聚醚氨酯,并制成了透明薄膜。ESCA研究表明醚键富集于膜表面,断裂伸长率均大于400％。并用复钙法测定了它们的抗凝血性能,对扩链剂中引入醚键对聚醚氨酯的性能的影响进行了讨论。     

路用单组分湿固化聚氨酯冷补液的制备与性能

为了制备一种新型的、有望代替沥青的单组分湿固化路用聚氨酯胶结料,优选聚氨酯冷补液反应单体异氰酸酯衍生物(液化MDI)、二苯基甲烷二异氰酸酯、多亚甲基多苯基异氰酸酯、聚氧化丙烯二醇、三羟基聚氧化丙烯醚,采用二月桂酸二丁基锡为催化剂、三羟甲基丙烷为扩链剂,通过设计不同材料组成、合成工艺,制备得到不同类型的单组分湿固化聚氨酯冷补液。通过聚氨酯的黏度、拉伸强度、断裂伸长率、邵氏硬度和拉拔强度测试,研究了原材料组成和合成工艺对聚氨酯路用性能的影响;通过红外光谱表征了聚氨酯的微观结构;通过测试聚氨酯混合料的马歇尔稳定度和膨胀率,确定了聚氨酯的最佳用量,以此作为基础制备了聚氨酯混合料研究其力学强度发展规律固化特性,并评价其路用性能。研究结果表明：异氰酸酯基/羟基物质的量比为7/2～9/2,聚氧化丙烯二醇/三羟基聚氧化丙烯醚的物质的量比为5/5～7/3,二月桂酸二丁基锡掺量(质量分数,下同)为0.1%、三羟甲基丙烷掺量为0.5%～1%、反应温度和搅拌速率分别为80℃～90℃和400～500 r/min时,异氰酸酯基与羟基成功的发生了反应,所合成的聚氨酯具有良好的力学强度和流动性。聚氨酯的掺量为集料用量...     

含氟聚氨酯的制备及性能研究

以二甲苯为溶剂,全氟聚醚二元醇和异佛尔酮二异氰酸酯（IPDI）为原料,1,4丁二醇（BDO）作为扩链剂合成了含氟聚氨酯（FPU）,通过改变软段全氟聚醚二元醇用量控制FPU的氟质量分数.并且以聚丙二醇（PPG）和异佛尔酮二异氰酸酯（IPDI）为原料,以1,4丁二醇（BDO）作为扩链剂合成了不含氟的聚氨酯（PU）作为对比.对PU与FPU的结构进行了表征,考察了氟质量分数对FPU热稳定性、力学性能以及疏水疏油性的影响.结果表明,制得的FPU具有更高的拉伸强度,同时在保持聚氨酯疏油性的同时,还获得了较好的疏水性.      

热塑型聚氨酯弹性体的极限断裂强发动力学模型理论

本文提出了一种等速拉伸下聚氨酯极限断裂强度动力学模型理论,它从聚氨酯大形变弹性理论出发,将单向拉伸应力-应变关系同应力集中链的断链动力学方程相结合,推导出了应力集中链的断链动力学方程,积分和化简后得到了极限断裂强度同断裂伸长,链结构参数和测试条件(温度和拉伸速率)间的定量关系式。在实验上又分别考虑了W_k,_(ns)、T和k_λ~·等对极限断裂力学性能的影响。并以大量实验数据对理论进行了验证,得到理论同实验较好地一致。成功地把聚氨酯网络结构同极限断裂力学性能联系起来,为预测聚氨酯极限断裂力学性能和建立它们的破裂包络线提供了理论基础。     

混合扩链剂对聚氨酯弹性体宏观性能的影响

以4,4′-二苯基甲烷二异氰酸酯（MDI）和聚四氢呋喃均聚醚（PTMG）为原料合成聚氨酯（PU）预聚体（A组分）,三羟基聚醚多元醇（330N）分别与1,4-丁二醇（BDO）或乙二醇（EGO）混合作为扩链剂（B组分）,将A、B组分聚合制备PU弹性体。探讨330N/BDO与330N/EGO不同体系以及各体系不同质量比对PU弹性体热性能和机械性能的影响。结果表明,330N/BDO体系的软段玻璃化转变温度（T_gs）较低,硬段熔融热较高,随着330N/BDO质量比的下降,T_gs 上升,硬段熔融热增加;330N/EGO体系的拉伸强度、硬度稍高,而断裂伸长率和滞后损失（tan δ ）有较大落差,随着330N/EGO质量比的下降,弹性体的拉伸强度和硬度增加,断裂伸长率和滞后损失降低。     

Collapse of stiff conjugated polymers with chemical defects into ordered, cylindrical conformations

The optical, electronic and mechanical properties of synthetic and biological materials consisting of polymer chains depend sensitively on the conformation adopted by these chains. The range of conformations available to such systems has accordingly been of intense fundamental as well as practical interest, and distinct conformational classes have been predicted, depending on the stiffness of the polymer chains and the strength of attractive interactions between segments within a chain. For example, flexible polymers should adopt highly disordered conformations resembling either a random coil or, in the presence of strong intrachain attractions, a so-called 'molten globule'. Stiff polymers with strong intrachain interactions, in contrast, are expected to collapse into conformations with long-range order, in the shape of toroids or rod-like structures. Here we use computer simulations to show that the anisotropy distribution obtained from polarization spectroscopy measurements on individual poly[2-methoxy-5-(2'-ethylhexyl)oxy-1,4-phenylenevinylene] polymer molecules is consistent with this prototypical stiff conjugated polymer adopting a highly ordered, collapsed conformation that cannot be correlated with ideal toroid or rod structures. We find that the presence of so-called 'tetrahedral chemical defects', where conjugated carbon-carbon links are replaced by tetrahedral links, divides the polymer chain into structurally identifiable quasi-straight segments that allow the molecule to adopt cylindrical conformations. Indeed, highly ordered, cylindrical conformations may be a critical factor in dictating the extraordinary photophysical properties of conjugated polymers, including highly efficient intramolecular energy transfer and significant local optical anisotropy in thin films.     

Rapidly recovering hydrogel scaffolds from self-assembling diblock copolypeptide amphiphiles

Protein-based hydrogels are used for many applications, ranging from food and cosmetic thickeners to support matrices for drug delivery and tissue replacement. These materials are usually prepared using proteins extracted from natural sources, which can give rise to inconsistent properties unsuitable for medical applications. Recent developments have utilized recombinant DNA methods to prepare artificial protein hydrogels with specific association mechanisms and responsiveness to various stimuli. Here we synthesize diblock copolypeptide amphiphiles containing charged and hydrophobic segments. Dilute solutions of these copolypeptides would be expected to form micelles; instead, they form hydrogels that retain their mechanical strength up to temperatures of about 90 degrees C and recover rapidly after stress. The use of synthetic materials permits adjustment of copolymer chain length and composition, which we varied to study their effect on hydrogel formation and properties. We find that gelation depends not only on the amphiphilic nature of the polypeptides, but also on chain conformations--alpha-helix, beta-strand or random coil. Indeed, shape-specific supramolecular assembly is integral to the gelation process, and provides a new class of peptide-based hydrogels with potential for applications in biotechnology.     

无溶剂法制备聚酯型水性聚氨酯及性能研究

以IPDI、聚酯/聚醚二元醇和二羟甲基丙酸为主要原料,乙二胺为扩链剂,采用无溶剂法成功制得分散良好、贮存稳定的水性聚氨酯乳液.通过FTIR及粒度分析仪对产物进行了表征,研究软硬段比例、软段结构对乳液胶膜机械性能、胶膜耐水性的影响.结果表明,随着软段比例的上升,链的柔性增加,耐水性提高;随着软段中加入聚酯含量的增加,机械强度提高,耐水性增强.     

正交法研究不同因素对SF/PU复合水凝胶抗压性能的影响

IPDI为硬段,PEG、PPG为软段,DMPA、DEG为扩链剂,TEA为中和剂合成了聚氨酯预聚体.以PEG的相对分子质量、-NCO/-OH(n/n)、 PEG/(PEG+PPG)(n/n) 和SF/(SF+PU)(m/m)为4个影响因素设计了四因素四水平正交实验并制备了一系列丝素蛋白/聚氨酯复合水凝胶.采用非限制性压缩试验对水凝胶进行抗压缩性能测试,并通过方差分析法对实验结果进行分析.结果表明PEG的相对分子质量对水凝胶的抗压性能影响最明显.PEG的相对分子质量为600、1 000、2 000、4 000时所制备的丝素蛋白/聚氨酯复合水凝胶的抗压模量均在0.35～1.20 MPa之间.     

Thermoelectric properties of p-type Bi-Sb-Te compositionally graded thermoelectric materials with different barriers

In order to find more suitable materials as barriers and to improve the thermoelectric properties, p-type (Bi_l-xSb_x)₂ Te₃ (x=0.85, 0.9) two segments compositionally graded thermoelectric materials (CGTM) with different barriers were fabricated by conventional hot pressure method. Metals Fe, Co, Cu and Al were used as barriers between two segments. The effects of different barriers on thermoelectric properties of CGTM were investigated. The results show that metal Fe is more stable and suitable as the barrier.     

共聚硬球链流体及其混合物的状态方程

将前文导得的均聚硬球链流体的分子热力学模型推广应用到共聚硬球链及其混合流体，用本模型预测的纯共聚硬球链流体和均聚硬球链流体混合物的压缩因子与计算机模拟结果比较，两者能很好地相互吻合，为进一步构筑实际高分子溶液和共混物的分子热力模型打下了良好的基础。     

Ferromagnetism in one-dimensional monatomic metal chains

Two-dimensional systems, such as ultrathin epitaxial films and superlattices, display magnetic properties distinct from bulk materials. A challenging aim of current research in magnetism is to explore structures of still lower dimensionality. As the dimensionality of a physical system is reduced, magnetic ordering tends to decrease as fluctuations become relatively more important. Spin lattice models predict that an infinite one-dimensional linear chain with short-range magnetic interactions spontaneously breaks up into segments with different orientation of the magnetization, thereby prohibiting long-range ferromagnetic order at a finite temperature. These models, however, do not take into account kinetic barriers to reaching equilibrium or interactions with the substrates that support the one-dimensional nanostructures. Here we demonstrate the existence of both short- and long-range ferromagnetic order for one-dimensional monatomic chains of Co constructed on a Pt substrate. We find evidence that the monatomic chains consist of thermally fluctuating segments of ferromagnetically coupled atoms which, below a threshold temperature, evolve into a ferromagnetic long-range-ordered state owing to the presence of anisotropy barriers. The Co chains are characterized by large localized orbital moments and correspondingly large magnetic anisotropy energies compared to two-dimensional films and bulk Co.     

直线链码和形式语言

本文给出并比较了有关直线链码性质的几种表述,证明了直线链码的一个性质:若将全体直线链码所组成的集CL看作是{0,1,2,3,4,5,6,7}上的语言,则CL是上下文有关的.由于CL不是上下文无关语言,直线链码集CL在语言类中的归属就被完全确定了.