由铜-胺氧化还原引发反应一步法简便制备TiO_2表面接枝聚甲基丙烯酸甲酯纳米杂化粒子

提出并验证了一种通过普通自由基聚合在纳米TiO2表面接枝聚甲基丙烯酸甲酯的简单方法.通过在纳米TiO2粒子表面引入伯胺分子层(纳米TiO2-NH2粒子),利用Cu2+-胺氧化还原体系实现了CuSO4催化纳米TiO2-NH2粒子表面引发甲基丙烯酸甲酯(MMA)的自由基接枝聚合,从而一步得到表面固定有聚甲基丙烯酸甲酯链的纳米TiO2杂化粒子(纳米TiO2-PMMA杂化粒子).红外光谱、热失重分析与电镜的结果都表明PMMA已经被接枝到纳米TiO2粒子表面,且接枝率随着聚合时间的延长而逐渐增大,PMMA链的引入有助于降低纳米TiO2粒子微球的团聚程度、增强与有机溶剂分子的范德华力,从而提高分散稳定性.反应溶液中没有游离均聚物形成.     

纳米AgBr/PMMA光致变色杂化材料制备与表征

采用本体聚合法制备了纳米AgBr/PMMA(聚甲基丙烯酸甲酯)光致变色杂化材料. XRD分析表明，纳米AgBr/PMMA杂化材料是无定形的. SEM分析表明， AgBr含量不同，杂化材料的断面形貌明显不同，随AgBr含量的增加，杂化材料由韧性断裂向脆性断裂转变. EDS面分析表明， Ag、Br元素在杂化材料中均匀分布.所制备的纳米AgBr/PMMA杂化材料具有一定的光致变色效应.     

聚甲基丙烯酸甲酯/二氧化硅杂化材料制备与性能

溶胶-凝胶;聚硅酸;聚甲基丙烯酸甲酯/二氧化硅杂化材料制备与性能     

阻燃剂9,10-二氢-9-氧杂-10-膦杂菲-10-氧化物合成中酯化反应和酰基化反应的优化

有机磷杂环化合物9,10-二氢-9-氧杂-10-膦杂菲-10-氧化物(DOPO)因性能优异而作为无卤阻燃剂得到广泛应用。为了提升和改进DOPO的合成,不少文献对合成中的4个反应,即酯化反应、酰基化反应、水解反应和关环反应进行了大量研究,但是由于缺少合适的分析方法和仪器,对酯化反应和酰基化反应仍没有得出明确的结论。本文则采用了核磁共振磷谱以及测量反应产物HCl吸收碱液的温度变化两种方法,精确地得到了酯化反应和酰基化反应的优化条件。首先采用核磁共振磷谱,讨论了酯化反应温度、原料配比和加料方式对酯化反应产物组成的影响,得出了邻苯基苯氧基二氯化磷(CC)含量高的工艺条件:反应温度80℃,PCl3过量25%~50%,采用邻苯基苯酚(OPP)加入PCl3的反滴法;并得出酯化反应产物的组成直接决定了6-氯-(6氢)-二苯并-(c,e)-氧磷杂己环(CDOP)在酰基化反应产物中的含量。另通过测量HCl吸收碱液的温度变化,间接表征酰基化反应的反应速度,由此得出合适的酰基化反应温度和催化剂用量。结果为:当催化剂固定为0.2 g时,酰基化反应在150℃几乎不反应,随温度升高,反应变快,180℃下4 h完全,190℃下1.5 h即可完成;温度180℃下,1~1.5 g/1 mol OPP的催化剂较为合适,酰基化反应在3~4 h结束。     

PMMA/TiO_2-SnO_2有机无机杂化材料的制备及表征

以乙酰丙酮为偶联剂,应用溶胶-凝胶法制备了聚甲基丙烯酸甲酯(PMMA)/TiO2-SnO2有机无机杂化材料。采用红外光谱(FT-IR)、紫外光谱(UV)对PMMA/TiO2-SnO2进行表征,并测定其TG性质。结果表明:在聚合反应过程中,有机聚合物和无机组分之间通过共价键相连,并且该杂化材料具有良好的抗紫外光辐射性能和热稳定性能。     

介孔二氧化硅-接枝胶原杂化材料的制备和表征(英)

利用接枝胶原与介孔二氧化硅制备一种新型生物无机杂化材料。用甲基丙烯酸甲酯为接枝剂对胶原进行共聚改性制得接枝胶原。以正硅酸乙酯为模板，十二烷基三甲基溴化铵为表面活性剂，用一个简单的热处理过程制得介孔二氧化硅。介孔二氧化硅-接枝胶原杂化材料通过超声分散接枝胶原与介孔二氧化硅的混合物制得，其三维结构用X射线衍射表征，晶格参数a，b和c分别为0.68，0.37和1.64 nm，为正交晶型。氮气吸附-解吸等温线显示杂化材料的比表面积可达273 m²·g^-1，孔体积为0.13 cm³·g^-1，平均孔径3.4 nm，分布窄。该杂化材料在8～14 μm波长的红外发射率可低至0.323，在光电子学器件和红外隐身领域具有潜在应用价值。     

磷系阻燃剂插层镁铝型水滑石复合物的制备及其在热塑性聚氨酯中的阻燃应用

采用直接的无溶剂制备方法,将3种磷系阻燃剂9,10-二氢-9-氧杂-10-磷杂菲-10-氧化物(DOPO)、聚磷酸铵(APP)和三聚氰胺聚磷酸盐(MPP)分别插层到镁铝型水滑石(MAH)片层中,制备了3种含磷阻燃剂的MAH复合物(DOPO-MAH、APP-MAH和MPP-MAH),并采用模压成型法制备了MAH复合物与热塑性聚氨酯(TPU)的复合材料。采用X射线衍射、扫描电子显微镜和热重分析分别对复合物进行了表征,并且通过锥形量热仪对复合材料进行了表征。结果表明,MAH中MPP的分散性较差,DOPO和APP的分散性较好,并且磷元素分布均匀。MAH的初始层间距为4.11 nm,APP和MPP均在0.5 h时就已完成插层,最终层间距分别缩小到3.93和4.04 nm。DOPO则在0.5 h后完成,但插层后的层间距更小,为3.86 nm。与物理混合物所制得的复合材料相比,(DOPO-MAH-6h)/TPU和(APP-MAH-6h)/TPU的热释放速率峰值分别从669.3 kW/m²降至573.9 kW/m²,从657.7 kW/m²     

新型含磷阻燃剂DOPO-PPO的合成及其阻燃性能

以苯基磷酰二氯,对羟基苯甲醛及9,10-二氢-9-氧杂-10-磷杂菲(DOPO)为原料,合成了一种新型含磷阻燃剂——二[4-(次甲基-羟基-磷杂菲)苯氧基]苯基氧化磷(DOPO-PPO),其结构经1H NMR和IR表征。通过TGA和DTG研究了DOPO-PPO的热稳定性,热降解行为及成炭性能。结果表明:DOPO-PPO的起始热分解温度为210℃,在700℃时残炭为30.4%。以环氧树脂为基材,DOPO-PPO为阻燃剂,二氨基二苯硫砜为固化剂,制备了阻燃环氧树脂(3)。通过极限氧指数(LOI)和垂直燃烧(UL-94)测试了3的阻燃性能。结果表明:当DOPOPPO的添加量为12.0%(质量百分数,即312)时,阻燃级别为V-0级,LOI为34.0%。     

利用聚合物乳液合成聚甲基丙烯酸甲酯/二氧化硅纳米杂化材料

通过正硅酸乙酯分别在聚甲基丙烯酸甲酯乳液和四氢呋喃溶液中的溶胶－凝胶反应制备出不同的聚甲基丙烯酸甲酯／二氧化硅复合材料。利用扫描电镜、透镜电镜、差热分析和热失重对试样进行了分析。结果表明，利用聚合物乳液可以获得纳米分散的聚甲基丙烯酸甲酯／二氧化硅复合材料，并且在某种程度上其分散尺度小于利用聚合物溶液获得的复合材料。同时，利用聚合物乳液来制备聚甲基丙烯酸甲酯／二氧化硅杂化材料更有利于凝胶过程中二氧化硅网络的形成。     

以膦酰杂菲为侧基的1-戊炔聚合反应及其结构与热力学性质

以2-(6-氧化-6-氢-二苯基(c,e)<1,2>氧杂膦酰基)-1,4-二羟基苯(ODOPB)结构单元为中心,在两侧通过酯化反应分别引入4-(4-戊炔氧基)苯甲酰基和4-丁氧基苯甲酰基,得到了1-戊炔衍生物单体M-34,同时合成了不含9,10-二氢-9-氧杂-10-膦杂菲-10-氧化物(简称膦酰杂菲,DOPO)基元的M-34模型化合物M-0.分别以[Rh(nbd)Cl]2和Rh(nbd)B(C6H5)4为催化剂,研究了催化剂浓度和聚合时间对M-34和M-0聚合反应收率的影响.结果表明,由于DOPO存在较大π共轭结构和较强极性效应,降低了催化剂的活性,使得聚合产物P-34分子量较低,但改善了P-34的溶解性,并诱导P-34主链基本采取全反式构型,从而有利于增强侧基之间的相互作用,使这种含有DOPO的聚1-戊炔衍生物呈现良好的热稳定性,且优于其不含DOPO模型聚合物P-0的热稳定性.但同时DOPO的引入也增加侧基的体积,为链段运动提供了较大的自由体积,使得P-34的Tg低于不含DOPO模型聚合物P-0的Tg.     

Synthesis of Macroporous PMMA/Silica Nanocomposite Monoliths in Supercritical Carbon Dioxide

Summary: Macroporous monoliths consisting of silica nanoparticles embedded in poly(methyl methacrylate) (PMMA) were synthesized in supercritical CO₂. Well‐dispersed silica particles, pretreated with functional 3‐(trimethoxysilyl)propyl methacrylate (MPS), were to form colloidal PMMA nanocomposites followed by a sol‐gel transition forming interconnected structures resulting in micron‐sized pores with specific areas between 1 and 7 m² · g⁻¹. SEM and TEM results revealed uniform morphological characteristics of the composite materials and good dispersions of the silica nanoparticles.

SEM micrograph of PMMA/Silica nanocomposites forming interconnected macroporous monolith. The average size of the silica particles is 50 nm.     

SiO2交联剂交联MMA聚合制备PMMA/SiO2纳米复合材料

用SiO2交联剂(SiO2HPA)交联甲基丙烯酸甲酯(MMA)自由基聚合制备PMMA SiO2纳米复合材料。采用两步法将可聚合乙烯基单体以化学键的形式键接到SiO2表面合成SiO2交联剂,首先利用过量的甲苯2,4二异氰酸酯(TDI)对SiO2纳米粒子表面进行化学修饰合成出表面带有高反应活性NCO基团的功能化SiO2粒子(SiO2TDI),SiO2TDI与丙烯酸羟丙酯(HPA)反应合成SiO2交联剂。系统研究了MMA单体与SiO2交联剂投料比及聚合时间对聚合反应的影响。此外,利用红外光谱(FT IR)、DSC、TGA、可见光光谱仪等实验手段对纳米复合材料进行了表征分析。结果表明,纳米SiO2粒子在复合材料中起着物理交联点和化学交联点作用,复合材料玻璃化转变温度(Tg)明显地高于其纯PMMA的玻璃化转变温度,随着纳米SiO2粒子含量的增加,复合材料玻璃化温度升高,而透明度明显降低。     

Effects of incorporation of modified silica nanoparticles on the mechanical and thermal properties of PMMA

Silica nanoparticles of various sizes have been incorporated by melt compounding in a poly(methyl methacrylate) (PMMA) matrix to enhance its thermal and mechanical properties. In order to improve nanoparticles dispersion, PMMA grafted particles have been prepared by atom transfer radical polymerization (ATRP) from well-defined silica nanoparticles. This strategy was expected to ensure compatibility between both components of the PMMA nanocomposites. TEM analysis have been performed to evaluate the nanosilica dispersion whereas modified and non-modified silica/PMMA nanocomposites thermal stability and mechanical properties have been investigated by both thermogravimetric and dynamical mechanical analysis.     

Combination effect of nanoparticles with flame retardants on the flammability of nanocomposites

Polystyrene based nanocomposites (PNCs) with and without flame retardant additives were successfully prepared through a single-screw extrusion technique. The combination effect of nanoparticles and flame retardants was investigated with nanosilica and attapulgite clay as nanofillers, and with a NASA formulated SINK flame retardant. A comprehensive study was done by Cone Calorimetry, UL94 and TGA.The addition of nanoparticles to polystyrene generally improved the OI of polystyrene. The horizontal burning tests suggested that nanofiller types have different impacts on the flammability of nanocomposites. According to the vertical burning tests and oxygen indices, it was found that polystyrene/silica and polystyrene/attapulgite clay PNCs alone are not flame retardant. In fact, the materials burned faster. However, the combination of nanocomposites with the SINK flame retardant significantly altered the thermal stability, and flammability of the materials. A remarkable reduction in heat release rates of polystyrene was achieved for both silica and attapulgite with flame retardant nanocomposites. For instance, the introduction of 20% SINK into PS reduced the PHRR of PS from 1212 to 838 (−31%); 10% silica reduced it from 1212 to 1060 (−13%), while the combination of silica and SINK reduced it to 530 (−56%), which clearly shows interaction between nanosilica and SINK.     

ENHANCED MECHANICAL PROPERTIES OF POLYPROPYLENE/SILICA NANOCOMPOSITES WITH SURFACE MODIFICATION OF NANO-SILICA VIA IN SITU COPOLYMERIZATION OF METHYL METHACRYLATE AND BUTYL ACRYLATE

Nano-sized silica particles were modified with methacryloxy-propyltrimethoxysilane(MPS) followed by in situ copolymerization of methyl methacrylate(MMA) and butyl acrylate(BA).These modified nanoparticles were compounded with polypropylene(PP) to prepare PP/silica nanocomposites.PMMA grafted on nano-silica enhances the dispersion of the nanoparticles and interfacial adhesion,decreases the size of PP spherulites in nanocomposites and leads to increasing the Young's modulus and toughness of PP/silica nanoc...     

Free volume holes diffusion to describe physical aging in poly(mehtyl methacrylate)/silica nanocomposites

The spontaneous thermodynamically driven densification, the so-called physical aging, of glassy poly(mehtyl methacrylate) (PMMA) and its nanocomposites with silica has been described by means of the free volume holes diffusion model. This mechanism is able to account for the partial decoupling between physical aging and segmental dynamics of PMMA in nancomposites. The former has been found to be accelerated in PMMA/silica nanocomposites in comparison to "bulk" PMMA, whereas no difference between the segmental dynamics of bulk PMMA and that of the same polymer in nanocomposites has been observed. Thus, the rate of physical aging also depends on the amount of interface polymer/nanoparticles, where free volume holes disappear after diffusing through the polymer matrix. The free volume holes diffusion model is able to nicely capture the phenomenology of the physical aging process with a structure dependent diffusion coefficient.     

Thermally stable polymer composites with improved transparency by using colloidal mesoporous silica nanoparticles as inorganic fillers

The colloidal mesoporous silica nanoparticles with small particle sizes (namely, CMS) are used as inorganic fillers of polymers (i.e. epoxy and silicone). From simple calculation, almost all polymers are estimated to be confined in the mesopores. To clarify the superiority of CMS over nonporous silica particles and mesoporous silica particles with much larger size (TMPS-4) as inorganic fillers, a systematic study on mechanical strength and transparency of polymer-silica nanocomposites was conducted. Compared with nonporous silica particles, similar to TMPS-4, CMS shows a greater effect on lowering the CTE. In addition, obtained polymer-CMS nanocomposites show improved transparency than polymer-TMPS-4 nanocomposites.     

Synthesis and characterization of poly(methylmethacrylate)/silica nanocomposites: Study of the interphase by solid‐state NMR and structure/properties relationships

Organic/inorganic nanocomposites were synthesized from poly(methylmethacrylate) (PMMA) and properly modified silica nanoparticles by in situ polymerization. Methacryloylpropyltrimethoxysilane was selected as nanoparticle surface modifier because it is characterized by unsaturated end groups available to radical reactions, making possible to suppose their participation in the acrylic monomer polymerization. As a result of the above hypothesized reactions, a phase constituted by polyacrylic chains grafted onto modified silica surface was isolated. ²⁹Si and ¹³C solid‐state nuclear magnetic resonance experiments permitted to analyze this phase in terms of composition and chain mobility as well as to highlight interaction mechanisms occurring between growing PMMA oligoradicals and functional groups onto silica surface. It was demonstrated that this PMMA grafted onto silica surface acts as an effective coupling agent and assures a good dispersion of nanoparticles as well as a strong nanoparticle/matrix interfacial adhesion. As a result of strong interactions occurring between phases, a significant increase of the glass transition temperature was recorded. Finally, the abrasion resistance of PMMA in the hybrids was significantly improved as a result of a different abrasion propagation mechanism induced by silica particles thus overcoming one of the most serious PMMA drawback. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010     

Transparent poly(methyl methacrylate)/TiO<Subscript>2</Subscript> nanocomposites for UV-shielding applications

Transparent poly(methyl methacrylate) (PMMA)/TiO₂ nanocomposites have been prepared by solution mixing PMMA with organically soluble titania xerogel. The organically soluble titania xerogel in the form of amorphous phase has been synthesized via a simple sol-gel method, involving hydrolysis of tetrabutyl titanate (TBT) in trifluoroacetic acid (TFA) and gelation. The obtained PMMA/TiO₂ nanocomposites were characterized by Fourier transform infrared spectroscopy (FTIR), transmission electron microscope (TEM), thermogravimetry (TG) and ultraviolet-visible (UV-vis) absorption spectroscopy. The results showed that the interaction between titania nanoparticles and PMMA macromolecular chains led to a homogeneous dispersion of TiO₂ in PMMA matrix. The resulting PMMA/TiO₂ nanocomposites showed improved thermal stability, high transparency and high UV-shielding efficiency with a small amount of titania xerogel (≤3.0 wt %). The present work is of interest for developing a series of transparent UV-shielding nanocomposites.     

Preparation and physical properties of flame retardant acrylic resin containing nano-sized aluminum hydroxide

Poly(methylmethacrylate) (PMMA) shows high strength and transparency but is a flammable material. In this study, the surface of aluminum hydroxide was modified with methacrylate containing phosphoric acid moieties before dispersion in MMA, and organic-inorganic nano-hybrid materials were obtained by bulk polymerization in the presence of the surface-modified aluminum hydroxide. The resulting hybrid materials retained the high transparency of PMMA, with transparency values similar to that of pure PMMA. Moreover, the flame resistance of the hybrid materials was improved in comparison with that of pure PMMA, with depression of the horizontal burning rate becoming a maximum at an inorganic content of 3 wt%. These results suggest that the use of aluminum hydroxide surface-modified with phosphoric acid groups is an efficient method for obtaining good performance fire-resistant polymer materials.