微乳液聚合和寡链高分子凝聚态研究进展

介绍了微乳液的结构，微乳液聚合，寡链高分子凝聚态和微胶乳粒子成膜过程的最新进展。     

聚苯乙烯胶乳颗粒的成膜过程及尺寸效应

聚合物乳液成膜过程可分为介质蒸发、颗粒形变和相邻颗粒间高分子的扩散融合三个阶段.一般认为,环境温度达到或高于高分子的玻璃化转变温度(T_g)时颗粒才可能发生形变.Goudy等研究了粒径为0.24～1.05μm的聚苯乙烯(PS)胶乳的成膜过程,发现PS颗粒在368K(T_g约373K)热处理很长时间也不发生形变,而在378K热处理后,粒径较小的颗粒融合速度快于较大颗粒.     

基板界面对PS/PMMA溶液共混物溶剂挥发成膜相结构的影响

研究了PS PMMA的共混物溶液溶剂蒸发成膜时的基板界面效应 .利用扫描电子显微镜 (SEM)研究了PS PMMA(5 5 ) (W W) THF高分子共混物溶液在不同基板上通过溶剂挥发成膜的相形态结构 .通过FTIR及ATR FTIR检测了共混物薄膜及其表面的共混组成 .研究结果表明 ,成膜基板对高分子共混物溶液成膜后的相形态有很重要的影响 .控制共混物溶液体系成膜过程中的动力学因素 ,可以调控出所设想的各种复杂的相结构形态     

高分子水胶乳成膜过程研究现状

主要阐述了高分子水胶乳成膜过程中颗粒所受的作用力,颗粒变形的理论模型和实验方法的研究现状,从而对高分子水胶乳稆的影响因素作了探讨。     

高分子固体电解质研究进展

由于具有质轻，成膜性好，易卷曲等许多无机材料不可比拟的优点，高分子固体电解质自本世纪７０年代初刚出现就引起了人们极大兴趣。十几年来，这一领域的研究一下受到普遍关注。本文综述了对高分子固体电解质的研究过程中，人们旨在改善其导电性能，力学性能等综合性质能提出的理论构想和进行的实际探索，介绍了一些研究高分子固体电解质的新方法，并对高分子固体电解质材料的研究方向和应用前景作了展望。     

室温自交联型聚丙烯酸酯纳米乳液的研究

本文分别用反应性乳化剂和常规乳化剂合成了室温自交联丙烯酸纳米乳液,并对其乳液的流变性能进行了研究,发现:反应性乳化剂所得乳液的表观粘度ηa、稠度系数K、零剪切粘度η0均比常规乳化剂所得乳液的增大。并用XPS对乳胶膜进行分析表明,反应性乳化剂在乳液的干燥成膜过程中不易向胶层表面迁移富集。与常规乳化剂体系的乳液相比,反应性乳化剂体系的乳液挥发速率快,吸水率低。并对两种乳液进行了粒径大小及分布的表征。     

水性涂料用聚丙烯酸酯微乳液的合成及其表征

低污染、低能耗的乳液涂料在建筑涂料中得到了广泛应用,具有核壳结构的聚合物乳液对胶膜的力学性能有较大的改善[1],微米(或纳米)级乳液具有优异的成膜性能,两者均是近年来高分子材料科学中发展十分迅速的新领域[2]。但微乳液聚合时乳化剂用量大,单体含量少。本文采用阴非离子复合乳化剂体系,单体预乳化工艺,种子乳液聚合法,通过正交实验优化聚合工艺参数及体系配方,合成了纳米级聚丙烯酸酯微乳液。并对乳液聚合物的粒径及分布、热性能、分子量及分布、结构等进行了表征。1　实验部分1 1　主要原料及乳液表征苯乙烯(St)、甲基丙烯酸甲…     

单分散聚苯乙烯乳液高温成膜过程的形态观察

单分散乳液指微粒具有相同化学组成、粒径及界面性质等特征的分散体系 ,因其颗粒均一 ,结构可调 ,赋予了其很多独特性质 ,广泛应用于计量、电子、生物、分析、医学、化工和信息等领域 .同时 ,单分散微粒体系作为研究原子或分子结晶过程的模型物 [1] ,在凝聚态物理中具有重要作用 .单分散乳液在一些条件下能排列成最大密堆积规整结构 ,从而赋予乳胶膜更优异的性能 [2 ] .因此 ,研究单分散乳液的成膜过程 ,在基础理论和实际应用中具有重要意义 .软的乳胶微粒玻璃化温度在室温附近 ,它们在常温下就可形变融合成膜 ,此时水蒸发速度较慢 ,乳液中…     

高分子阻尼涂料的研究进展

介绍了高分子阻尼涂料的阻尼机理和组成,以及阻尼涂料的高分子改性方法,包括共聚、共混和互穿网络(IPN)等以及国内外发展现状。重点介绍了目前通用的树脂基料和填料,详细介绍了互穿网络改性方法和乳液聚合物互穿网络,以及环境友好水性阻尼涂料的研究现状和发展。     

取代聚吡咯自掺杂导电机理的理论研究

自掺杂导电高分子材料均溶于水,其水溶液容易在各种基质上浇注成膜,且加工方便,因而引起了人们的极大兴趣,然而有关其理论研究尚未见报道。 聚3-甲基-4-羧酸吡咯(PMPC)是水溶性自掺杂导电高分子材料中的一种,它可由3-甲基     

Film formation from pure and mixed latices; transient fluorescence study

A fast transient fluorescence technique was used to study latex film formation induced by organic solvent vapor. Mixtures of pyrene (P)- and naphthalene (N)-labeled and/or pure naphthalene-labeled latex films were prepared separately from poly(methyl methacrylate) (PMMA) particles. Then these pure and mixed latex films were exposed to vapor of various chloroform-heptane mixtures in seven different experiments. In both films, fluorescence lifetimes from N were monitored during vapor-induced film formation. It was observed that N lifetimes decreased as the vapor exposure time is increased. A Stern-Volmer kinetic analysis was used for low quenching efficiencies to interpret the decrease in N lifetimes. A Prager-Tirrell model was employed to obtain back-and-forth frequencies, nu, of reptating PMMA chains during latex film formation induced by solvent vapor. In both pure and mixed latex films, nu values were found to be correlated with the chloroform content in the vapor mixture. It was observed that polymer interdiffusion obeyed a t1/2 law during film formation.     

Effect of the acrylic acid content on the permeability and water uptake of poly(styrene-co-butyl acrylate) latex films

In this contribution, a theoretical modeling of the latex film formation is presented and compared to experimental results: water vapor permeability and latex film capacitance are studied as a function of acrylic acid content in poly(styrene-co-butyl acrylate) latex films. It has been shown that both water uptake and water vapor permeability are mainly affected by film morphology which in turn is defined by intercolloidal interaction and drying rate.     

Latex film formation studied with the atomic force microscope: Influence of aging and annealing

The surface structure of latex dispersion films was examined with an atomic force microscope. All measurements were done in air on latex films having a minimum film formation temperature of 12°C and a glass transition temperature of 18°C. One aim of this study was to follow structural changes during film formation. Three minutes after spreading the film, its surface layer dried. Afterwards, the structure of the film did not change anymore. Only after 4 months could structural changes be observed: Though individual latex particles could be identified, the particles partly melted into one another.After annealing films at 50° or 60°C for 4 h, the latex particles partly melted into one another, but individual particles could still be identified. When annealing at or above 80°C, no individual latex particles were visible anymore. With increasing temperature the film roughness decreased from 3 nm without annealing to 0.8 nm at 100°C annealing temperature. In addition, islands of 2–4 nm thickness appeared on the film surface. These islands could be scraped off the film by increasing the force between tip and sample, indicating that they are composed of surfactant which was squeezed out of the film.     

Latex film morphology and electrical potential pattern dependence on serum components: a scanning probe microscopy study

Dry films formed by surfactant-stabilized, peroxide-initiated styrene-butyl acrylate latex were examined by atomic and electric force microscopy (AFM and EFM). The effects of latex serum components on the films were observed by subjecting the latex to extensive dialysis prior to film formation, and comparing the results to as-prepared latex. The films formed with the dialyzed latex are smoother (as evidenced by roughness and fractal dimension measurements) than the films from the as-prepared latex, but they display large electric force gradients between neighboring domains. The films made with the as-prepared latex have the highest electric uniformity, with a maximum potential variation lower than 80 mV, while this reaches 200 mV in the dialyzed latex film.     

Site percolation model for latex film formation in soft polymer matrix

The UV-visible (UVV) technique was used to monitor latex film formation in a soft polymer matrix. Various film samples were prepared by increasing the amount of poly(methyl methacrylate) (PMMA) particles in a poly(isobutylene) (PIB) matrix. These samples were then annealed above the glass transition temperature to promote latex film formation. Transmitted photon intensities, Itr, were measured for each film. It is observed that Itr decrease as the latex content is increased, which was explained by the increase in scattered light intensity, Isc. The drastic increase in Isc above a certain latex content is attributed to the site percolation of latex particles in the PIB matrix. The percolation threshold and the critical exponent were measured and found to be 0.3 and 0.4, respectively. The increase in Itr by annealing of film samples above Tg was explained with the void closure process below 0.8 occupation probability. When the film is occupied completely with the latex particles, interdiffusion of polymer chains was observed. Viscous flow and chain diffusion activation energies were determined and found to be 8 and 51 kcal/mol, respectively.     

EFFECT OF SURFACTANTS ON FILM FORMATION OF POLY (VINYL ACETATE) AND POLY (VINYL ACETATE-BUTYL ACRYLATE) LATEXES

Effect of ethoxylated nonyl phenol type non-ionic and alkyl sulfate type anionic surfactants on the film formation process of poly (vinyl acetate) and poly (vinyl acetate-acrylate) latexes are discussed. HLB value of non-ionic surfactant is shown to affect glass transition temperature, minimum film formation temperature and rate of film coalescence of vinyl acrylic latexes. Higher HLB non-ionic surfactant appears to be more compatible than the lower HLB ones with the fairly polar vinyl acrylic latex and form a well coalesced film. Presence of sodium lauryl sulfate in the latex is observed to result in incompatible regions on the latex film surface, typical of two phase morphology. Influences of surfactants on the film formation process in the polar vinyl acrylic latexes are compared and contrasted with the available data on the effects of surfactants in styrene butadiene latexes. The findings are discussed in terms of adsorption and interaction behavior of surfactants at polar vinyl acrylic latex surfaces and current theories of latex film formation mechanisms.     

Fast transient fluorescence technique (FTRF) for studying vapor-induced latex film formation

A fast transient fluorescence (FTRF) technique was used to study latex film formation induced by organic solvent vapor. Seven different films with the same latex content were prepared separately from poly(methyl methacrylate) (PMMA) particles and exposed to vapor of various chloroform-heptane mixtures in seven different experiments. Latex films were prepared from pyrene (Py)-labeled latex particles and fluorescence lifetimes of Py were monitored during vapor-induced film formation. It was observed that pyrene lifetimes decreased as vapor exposure time increased. A Stern-Volmer kinetic analysis was used for low quenching efficiencies to interpret the decrease in pyrene lifetimes. A Prager-Tirrel model was employed to obtain back-and-forth frequencies, nu, of the reptating PMMA chains during latex film formation induced by solvent vapor. nu values were found to be correlated with chloroform content in vapor mixture. It was observed that polymer interdiffusion obeyed a t(1/2) law during film formation. The results of optical transmission experiments were found to support these findings.     

Temperature and relative humidity dependency of film formation of polymeric latex dispersions

Thermogravimetric analysis and a synchrotron small-angle X-ray scattering technique were employed to characterize the structural evolution of a polymeric latex dispersion during the first three stages of film formation at different temperatures and relative humidities. Three intermediate stages were identified: (1) stage I*, (2) stage I**, and (3) stage II*. Stage I* is intermediate to the conventionally defined stages I and II, where latex particles began to crystallization. The change of drying temperature affects the location of the onset of ordering, whereas relative humidity does not. Stage I** is where the latex particles with their diffuse shell of counterions in the fcc structure are in contact with each other. The overlapping of these layers results in an acceleration of the lattice shrinkage due to a decrease of effective charges. Stage II* is where the latex particles, dried well above their T(g), are deformed and packed only partially during film formation due to incomplete evaporation of water in the latex film. This is because of a rapid deformation of the soft latex particles at the liquid/air interface so that a certain amount of water is unable to evaporate from the latex film effectively. For a latex dispersion dried at a temperature close to its minimum film formation temperature, the transition between stages II and III can be continuous because the latex particles deform at a much slower rate, providing sufficient surface area for water evaporation.     

Glass transition and film formation of VeoVa/vinyl acetate latices; role of water and co-solvents

The physical forces causing deformation of latex particles during the film formation process have been witley studied. However, the forces resisting particle deformation are still poorly characterized. It is clear that the extent of particle deformation is dependent on the viscoelastic nature of the polymer. In an emulsion, the latex particles will normally contain water, surfactants and “free” monomers which lead to plasticization of the polymer. Although this effect has been recognized, so far it has been studied only on films that had been dried and then partially or completely swollen by water. In this work, plasticization of the emulsion polymers by water and co-solvent has been quantified via differential scanning calorimetry investigation directly on the aqueous latex dispersions. More specifically, the plasticizing effect of water on VeoVa/vinyl acetate copolymer latices and its influence on minimum film-forming temperature (MFFT) has been studied. A linear correlation has been found between T_g and MFFT for the wet latices. This new direct method should help to improve our understanding of the forces resisting latex film formation. Additionally, the homogeneous distribution of the hydrophobic and hydrophilic monomers (VeoVa and vinyl acetate respectively) in the latex particles was verified via a ¹³C-NMR (nuclear magnetic resonance) study performed directly on the latices. This study confirmed that no significant core/shell type of morphology had influenced latex film formation.     

Thermoanalytical and morphological studies of cross-linked latex films by advanced techniques

In the present report, thermal analysis (TMDSC, DMA, TG, stress-strain analysis), nano-indentation and AFM morphological characterization of cross-linkable latexes, prepared with either a pre-coalescence cross-linker (1,3-butylene glycol dimethacrylate) or post-coalescence cross-linker (adipic dihydrazide) at various levels of cross-linking, were done. The study assesses the effect of type and level of cross-linking on the film formation process through the evolution of mechanical properties and latex morphology. In addition, the final fundamental thermal and mechanical properties, specific end-use properties and latex morphology resulting from the film formation process are reported.