聚烯烃接枝改性设备的开发

介绍了近年来聚烯烃接枝工艺及其设备的开发情况。分别介绍了熔融接枝、溶液接枝、固相接枝、紫外光辐射接枝、等离子体接枝、超临界二氧化碳接枝的工艺及设备的开发情况。     

超临界CO2在高分子合成与制备中的应用

介绍超临界二氧化碳流体作为介质在高分子合成与制备中的研究进展。文中表明，可在超临界二氧化碳中实施氟代单体的自由基溶液聚合、甲基丙烯酸甲酯的分散聚合、丙烯酸的沉淀聚合、丙烯酰胺的反相乳液聚合以及异丁基乙烯基醚的阳离子聚合等多种聚合反应，可用超临界二氧化碳溶胀聚合法制备梯度共混物。此外，超临界二氧化碳还可用于聚合物分级和聚合物微孔、微纤与微球材料的制备等，显示出超临界二氧化碳是一种对环境无污染且价廉的     

超临界二氧化碳中含氟聚合物的合成

超临界二氧化碳是廉价、低毒、不易燃、易回收、环境友好的惰性聚合介质,是传统有机溶剂的替代品。尤其是有望成为含氟单体的聚合溶剂,以替代目前使用的氟氯烃。本文详细地介绍了近年来以超临界二氧化碳为介质的氟烷基丙烯酸酯类单体和氟烯烃类单体的聚合反应研究,其中涉及氟烷基丙烯酸酯类单体的均聚和共聚,可熔融加工的四氟乙烯聚合物,离子交换树脂,偏氟乙烯的均聚和共聚合等。研究表明在超临界二氧化碳中的含氟单体的聚合反应有其它溶剂体系无法比拟的优点。     

聚苯乙烯／顺丁橡胶接枝苯乙烯共混过程光散射研究

聚合物共混物共混过程结构发展的研究较多［’－‘j，一致结论是分散相尺寸的迅速降低主要发生在最初1．5min到2min．当材料处于熔融或软化过程时，结构将发生极大的变化．材料在共混中往往出现薄片状或带状结构，基本处于微米尺度．本文利用X光小角散射、激光背散射及扫描电镜分别从微米尺度和纳米尺度对共混过程中微观结构的动态变迁进行了讨论聚苯乙烯（PS，民一5．8X10’，风一2．7XIO5，密度1．05，北京燕山石化公司生产）与顺丁橡胶接枝苯乙烯（PCBR－g－St，本实验室采用溶液接枝合成，接技率7．l％）按照80／20（质量比）比例…     

在超临界CO_2中进行的PP固相接枝改性研究进展

由于性价比高,聚丙烯(PP)成为增长最快的通用塑料,在汽车工业、家用电器和管材方面得到了广泛地应用。然而由于聚丙烯自身的非极性限制了其在某些领域的应用,向聚丙烯主链上接枝极性单体是改善其极性的有效方法。常用的接枝改性方法有:溶液接枝、熔融接枝、等离子体处理、表面可控活性聚合以及超临界CO2状态下接枝等。其中超临界CO2由于溶解单体能力强,对聚合物基体也有很好的溶胀能力,且阻燃性好、无毒以及价格相对低廉,克服了传统接枝方法存在的操作工艺复杂,溶剂不易回收等缺点,得到了广泛研究。本文从超临界CO2协助固相接枝改性机理、接枝单体的选择、影响过程的因素以及超临界CO2协助固相接枝的应用等方面出发,系统阐述了超临界CO2协助PP固相接枝改性近些年来的研究概况。     

酸酐化聚砜对聚砜/液晶聚合物共混物的界面增容作用

首先合成了马来酸酐接枝改性聚砜.改性后聚砜材料的表面张力增大,其中的极性分量增加明显,并以此增容聚砜/液晶聚合物(VectraB950)为原位复合体系,研究了增容前后共混物的加工流变行为和界面性能.结果表明,酸酐化聚砜可增强聚砜与液晶聚合物之间的界面作用,引起共混物加工粘度的上升;漫反射FTIR研究表明,增容后共混体系中的特殊相互作用增大;XPS和PLM的研究表明,在熔融加工过程中改性聚砜与液晶聚合物组分之间存在一定的界面化学反应,并生成了接枝共聚物.共混物相容性的提高应归结于相间化学反应与物理作用共同作用的结果.     

聚乙二醇双丙烯酸酯在超临界二氧化碳中的光聚合研究

探索了聚乙二醇双丙烯酸酯在超临界二氧化碳中发生光聚合反应制备聚合物颗粒的过程.方法为向充满超临界二氧化碳的高压反应釜中,同时喷射二氧化碳与聚乙二醇双丙烯酸酯及光引发剂的溶液,溶液与二氧化碳形成均匀的喷雾并进一步通过反溶剂作用与超临界二氧化碳形成分散体系,当同步进行紫外光照射时,单体可以在超临界二氧化碳中发生光聚合.结果证明此方法是可行的,得到了聚合物微颗粒.研究了不同溶剂及反应原料用量对产物粒径分布的影响.采用不同溶剂,将改变反应原料及产物在超临界二氧化碳中的溶解度,进而改变产物的粒径分布;反应原料用量增加,其在超临界二氧化碳中的溶解度减小,导致产物粒径分布较宽。     

反应性单体改性PP/PS共混物结晶与熔融行为

制备了三种反应性单体和两种PP接枝物改性的PP／PS共混物,用DSC研究了改性PP／PS共混物的结晶与熔融行为。结果表明：PS的加入提高了PP的结晶温度,两种接枝物的加入进一步提高共混物中PP的结晶温度,少量反应性单体对结晶温度影响不大,但高用量时则明显提高共混物的结晶温度;外加接枝物或者反应性单体对共混物中PP的熔融温度影响不大,但是熔融峰形与结晶温度高低有关。     

聚丙烯熔融接枝中共单体的作用机理

聚丙烯树脂是当今最具发展前途的热塑性高分子材料之一,在聚烯烃与工程塑料,如与聚酰胺或聚酯的共混合金中,聚丙烯接枝共聚物则广泛地被用为相容剂．此外,聚丙烯接枝共聚物还广泛应用于极性添加物等,用于改善制品的表面喷涂性能．聚丙烯接枝共聚物是通过自由基熔融接...     

聚丙烯多单体熔融接枝及其共混物研究

概括了聚丙烯多单体熔融接枝及其共混物的研究及发展状况,总结了现阶段对多单体熔融接枝机理的研究现状,并提出需要进一步解决的问题。     

Organosilicon compounds in supercritical carbon dioxide: Synthesis,polymerization, modification,and production of new materials

The main promising opportunities for the advantageous combination of organosilicon compounds and supercritical carbon dioxide both as a solvent and as a reagent in chemical processes are analyzed. The main processes of polymerization and modification of polymer matrices that are performed in supercritical СО₂ with the use of organosilicon materials of various types are outlined. Methods for the obtaining organosilicon polymers and polymer-inorganic composites and methods for the application of siloxane stabilizers in the dispersion polymerization of monomers in supercritical СО₂ are described. Studies of the insertion of a СО₂ molecule into Si–H, Si–N, and Si–O–Me bonds in reactions that feature exceptionally high chemical selectivity and afford a wide spectrum of products potentially useful for application in the chemistry of polymer materials are considered. It is shown that the silylation of surfaces of various types and morphologies in the medium of supercritical СО₂ is a rapidly developing green approach that makes it possible to obtain highly uniform defect-free coatings with variable desired functionality.     

Homogeneous and heterogeneous free radical polymerizations in environmentally responsible supercritical carbon dioxide

Fluoropolymers are used in many technologically demanding applications because of their balance of high-performance properties. A significant impediment to the synthesis of variants of commercially available amorphous fluoropolymers is their general insolubility in most solvents except chlorofluorocarbons (CFCs). The environmental concerns about CFCs can be circumvented by preparing these technologically important materials in supercritical fluids (SCFs). The homogeneous solution homo- and copolymerization of highly fluorinated acrylic, styrenic and olefinic monomers in supercritical carbon dioxide using free radical methods will be discussed [Science, 257 , 945 (1992)]. Detailed decomposition rates and efficiency factors will be presented for azobisisobutyronitrile (AIBN) in supercritical carbon dioxide and will be compared to conventional liquid solvents [Macromolecules, 26 , 2663 (1993)]. Additionally, viscosities of polymer solutions in supercritical CO₂ have been measured using a high pressure, falling cylinder viscometer. The results show that the polymer solution viscosities in supercritical CO₂ are an order of magnitude lower than with the same polymers in conventional organic solvents. The results from these homogeneous solution polymerization studies has allowed us to also consider heterogeneous polymerizations in a carbon dioxide continuous phase. Conventional emulsion polymerizations of unsaturated monomers are performed in either aqueous or organic dispersion media with addition of surface active agents (surfactants) to stabilize the colloidal dispersion that forms. With free radical initiators that are preferentially soluble in the continuous phase, high rates of polymerization and high molar mass polymers can be obtained simultaneously. Herein we describe an environmentally responsible alternative to aqueous and organic dispersing media for emulsion polymerizations which utilizes supercritical carbon dioxide, in conjunction with molecularly engineered free radical initiators and amphiphilic molecules that are specifically designed to be interfacially active in CO₂. Conventional lipophilic monomers, exemplified by methyl methacrylate and styrene, can be polymerized heterogeneously using a fluorinated azo-initiator in supercritical CO₂ in the presence of added surfactant to form stable emulsions that result in submicron size particles. Detailed surfactant and initiator syntheses and phase behavior will also be discussed.     

超临界CO2中的高分子合成研究进展

本文介绍以超临界CO₂流体为介质的高分子合成的研究进展。说明可在超临界二氧化碳中实施氟代单体的自由基溶液聚合、甲基丙烯酸甲酯和苯乙烯的分散聚合、丙烯酸的沉淀聚合、丙烯酰胺的反相乳液聚合以及异丁基乙烯基醚的阳离子聚合等多种聚合反应。这显示出超临界CO₂是一种对环境无污染且价廉的替代溶剂。     

超临界CO2协助三单体接枝改性聚丙烯

利用超临界二氧化碳(SC CO2)作为单体的溶剂和聚丙烯的溶胀剂, 通过自由基接枝聚合合成了聚丙烯与丙烯酸、甲基丙烯酸甲酯以及马来酸酐的接枝产物PP-g-(AA-MMA-MAH). 在单体的选择上采取软、硬单体复配的方式来调节链的柔韧性. 考察了溶胀条件、接枝条件以及单体配比对接枝反应的影响, 研究结果表明, PP和单体以及引发剂在7.74 MPa、47 ℃下溶胀5 h后, 75 ℃下反应3 h时接枝率为4.31%, 接枝效率可达71.83%. 产品表征说明单体均匀地接枝到聚丙烯颗粒上; 改性后聚丙烯水润湿角降低, 亲水性能得到明显改善; 接枝单体的引入提高了PP的热稳定性.     

Fabrication of flowerlike polymer superstructures using polymer/zeolite composites prepared with supercritical CO2

We report a route to the fabrication of unique flowerlike polymer superstructures with uniform petals at the nanoscale. In this method, polymer/zeolite composite is first prepared by loading corresponding monomer and initiator into the channels of the host zeolite with the aid of supercritical (SC) CO2, followed by thermal polymerization of monomers in the channels of the zeolite. The resultant polymer/zeolite composite is then treated with HF aqueous solution to allow the self-aggregation of the polymer and the inorganic components to form the polymeric layers and inorganic layers. Unique microscale flowerlike polymer superstructures are obtained after further treatment with HF aqueous solution. Different techniques, such as scanning electron microscopy (SEM), X-ray diffraction (XRD), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), and thermogravimetry (TG), have been used to characterize the microflowers.     

接枝改性碳酸钙及其在聚合物中的应用研究

介绍了近年来碳酸钙表面接枝改性的研究进展,讨论了自由基接枝聚合、辐照接枝聚合和力化学表面接枝聚合及偶联剂预处理与辐照并用接枝聚合改性方法。其中重点讨论了最新研究的偶联剂预处理与辐照并用接枝改性纳米碳酸钙的方法。用此方法制备的聚合物/纳米碳酸钙纳米复合材料在其他力学性能基本不变的情况下,大幅度提高了其缺口冲击强度和断裂伸长率。指出了碳酸钙表面接枝改性应向着提高接枝单体量和采用弹性体单体方面发展。     

Synthesis of Functional Polymers by Post‐Polymerization Modification

Post‐polymerization modification is based on the direct polymerization or copolymerization of monomers bearing chemoselective handles that are inert towards the polymerization conditions but can be quantitatively converted in a subsequent step into a broad range of other functional groups. The success of this method is based on the excellent conversions achievable under mild conditions, the excellent functional‐group tolerance, and the orthogonality of the post‐polymerization modification reactions. This Review surveys different classes of reactive polymer precursors bearing chemoselective handles and discusses issues related to the preparation of these reactive polymers by direct polymerization of appropriately functionalized monomers as well as the post‐polymerization modification of these precursors into functional polymers.     

Synthesis of soluble polymeric photosensitizers with the 4-nitro-1-naphthyl-carbamoyl as pendant group

Several models of monomers, homopolymers, and copolymers containing a photosensitizer group, 4-nitro-1-naphthyl-carbamoyl (NNC), have been synthesized. Synthetic methods are described, in addition to two routes for copolymers preparation. First, the radical copolymerization between monomers with the photosensitizer group built-in and comercial monomers such as styrene and methyl acrylate and, second, polymer modification by nucleophilic reaction between carbonyl group polymer supported and nitro-naphthyl amine. All products were characterized and one of the resulting soluble polymeric photosensitizer and its model compound, were tested as triplet energy donors against trans- stilbene and their Stern–Volmer constants were determined. Results show that the sensitizer efficiency is closer to that of the well known benzophenone sensitizer and higher than that of the acetophenone, while the sensitizer efficiency disminished when the chromophore is bonded to the polymer.     

生物催化在高分子合成中的应用

生物催化剂已被越来越多地用于高分子学中,产生了许多新的反应、工艺和商业用途.酶和全细胞工艺都引起了众多关注,生物催化剂的立体选择性是它们的主要优势之一,新的或改良的方法层出不穷.生物催化的进程主要集中在几个方面上:聚合反应、聚合物修饰反应、聚合物降解反应以及单体和低聚物的合成.在这篇文章中,我们总结了生物催化在高分子合成中的最新应用.