甲基丙烯酸3-三甲氧基硅丙酯/苯乙烯细乳液共聚合过程中的水解及缩合反应

研究了甲基丙烯酸3-三甲氧基硅丙酯(MPS)和苯乙烯(St)细乳液聚合过程中的水解及缩合反应.用气相色谱仪测定聚合过程中水解产物——甲醇的含量来研究MPS的水解度.MPS分子主要在细乳液液滴与水的界面以及乳胶粒与水的界面上发生水解反应.MPS和St比例、介质pH值、乳化剂用量、引发剂类型和用量都会影响MPS的水解程度.缩合产物用29Si固态核磁共振表征,中性条件下,缩合反应受到抑制,在高MPS/St比例的体系中也只生成少量缩合产物.酸性和碱性条件下,缩合产物量均增加,但碱性条件下,体系中仍有一定数量未缩合的硅氧烷存在,这与细乳液聚合独特的液滴成核机理及聚合过程中较少液滴间物质交换有关.     

甲基丙烯酸-3-三甲氧基硅丙酯/苯乙烯共聚乳胶粒微结构

我们曾制备了核-壳结构的杂化乳胶粒, 并用溶剂将核去除得到杂化空心微胶囊. 但由于此乳液聚合过程十分复杂, 在不同条件下反应得到乳胶粒的微结构有较大不同, 目前尚未见到各反应条件下所得产物微结构的表征和形成机理的研究报道. 本文将系统分析在不同反应条下, MPS和St种子乳液聚合过程中, 得到的乳胶粒壳层杂化聚合物的微结构, 并研究了其形成原因.     

水溶性和油溶性引发剂引发γ-甲基丙烯酰氧基丙基三甲氧基硅烷/苯乙烯细乳液共聚合的比较

分别用水溶性的过硫酸钾(KPS)和油溶性的2,2′-偶氮二异丁腈(AIBN)为引发剂引发γ-甲基丙烯酰氧基丙基三甲氧基硅烷(MPS)/苯乙烯(St)细乳液共聚合反应.比较了两类引发剂对MPS/St共聚合动力学(包括硅氧烷水解动力学和MPS/St的自由基共聚合动力学)、乳胶粒稳定性和共聚产物微结构的影响.     

α-氰基苄基碳负离子钠盐与碳酸二乙酯的单电子转移反应动力学和机理

测定了α-氰基苄基碳负离子钠盐与碳酸二乙酯缩合反应产物的结构及其分布,反应中间体的EPR谱,反应过程中产物和溶剂的CIDNP效应和反应动力学,为这一缩合反应提出了单电子转移-负离子自由基分解-自由基偶合的非链式自由基机理     

α-氰基苄基碳负离子钠盐与碳酸二乙酯的单电子转移反应动力学和机理

测定了α-氰基苄基碳负离子钠盐与碳酸二乙酯缩合反应产物的结构及其分布,反应中间体的EPR谱,反应过程中产物和溶剂的CIDNP效应和反应动力学,为这一缩合反应提出了单电子转移-负离子自由基分解-自由基偶合的非链式自由基机理。     

二氧化硅纳米粒子表面修饰及其表征

采用溶胶-凝胶法合成粒径在50—150nm范围内的二氧化硅（SiO2）纳米粒子。用甲基丙烯酸-3-（三甲氧基硅基）丙酯（MPS）对SiO2纳米粒子表面进行修饰,使其表面接枝能参与自由基聚合反应的碳碳双键基团。用元素分析、FTIR、^13C CP／MASNMR和^29Si CP／MASNMR等手段对修饰过的SiO2纳米粒子进行表征,以确证MPS接枝在SiO2纳米粒子上。分析修饰过的SiO2纳米粒子的^29Si CP／MASNMR和FTIR谱图,还可初步推断MPS接枝在SiO2纳米粒子表面的机理：MPS首先发生水解缩合反应形成低聚物,然后通过氢键作用吸附到SiO2纳米粒子表面,最后MPS低聚物中未缩合的硅羟基与SiO2纳米粒子表面的硅羟基发生缩合反应。     

不同尺寸（0.02—0.5μm）单分散聚苯乙烯乳液微球的制备

通过对苯乙烯乳液聚合微观动力学以及聚合过程中胶粒直径及其分布随时间变化的理论分析,并通过实验验证,比较了不同乳化剂种类、不同反应温度和不同单体用量条件下,产物胶乳的粒径分布,发现乳液聚合最终产物的粒径分布与成核期长短没有直接联系,而是取决于自由基进入胶粒的速率常数、稳态增长时间、胶粒中的平均自由基数目和胶粒的体积增长速率,胶乳单分散性随这些参量的增大而提高,从而解释了采用高温、高引发剂浓度以及长时间反应的条件对最终的胶粒尺寸分布的影响。本文还通过实验,找到了在20～500nm范围内控制粒径大小及粒径分布的方法。在20～100nm的范围内,用一步法乳液聚合,通过改变单体用量和乳化剂浓度,制备了一系列粒径的单分散聚苯乙烯胶乳;在100～500nm的范围内,运用种子乳液聚合,通过改变溶胀单体与种子胶乳的用量比,也制得了不同粒径的单分散聚苯乙烯胶乳。     

氧化-还原低温引发苯乙烯/丙烯酸丁酯细乳液共聚合动力学与成核机理的研究

详细讨论了 [(NH4 ) 2 S2 O8/NaHSO3 ]氧化 还原引发体系引发苯乙烯 (St)丙烯酸丁酯 (BuA)体系的细乳液共聚合的动力学特征及其与成核机理的关系 .细乳液的聚合速率比相同条件下的常规乳液聚合速率低 ,引发期长 .随聚合温度、引发剂浓度、乳化剂浓度的增加 ,聚合速率增大 .共乳化剂正十六烷 (HDE)的浓度在一定范围内增大 ,反应的速率增大 ,然后再增加HDE ,反应速率下降 .建立动力学曲线数学模型 ,并深入讨论了细乳液的聚合动力学特征 ,与常规乳液所得结果相比较 ,探讨了细乳液的单体液滴成核机理 .     

甲基丙烯酸甲酯-甲基丙烯酸无规共聚物的合成及其在乳液聚合中的应用

通过自由基共聚制备了不同组成的甲基丙烯酸甲酯-甲基丙烯酸无规共聚物,用碱中和后作为大分子乳化剂用于乳液聚合.研究了无规共聚物的组成、用量及反应温度对乳液聚合的影响.结果表明,在相同的反应条件下,乳化剂中聚甲基丙烯酸含量越多,乳液聚合速率越快;同一乳化剂,随乳化剂浓度的增加,乳液聚合速率增加;在乳化剂组成、浓度不变的情况下,反应温度越高,乳液聚合速率越大.     

酶促开环聚合与自缩合乙烯基共聚合相结合制取超支化聚合物

在Novozyme 435脂肪酶催化下, 甲基丙烯酸羟乙酯(HEMA)引发己内酯(ε-CL)开环聚合反应, 得到一端为双键, 另一端为羟基的直链聚己内酯(PCL)产物; 将其端羟基官能化得到大分子AB*型单体, 与苯乙烯以原子转移自由基聚合(ATRP)反应形式进行自缩合乙烯基共聚合, 得到超支化结构聚苯乙烯-b-聚己内酯产物.     

Self‐assembly of block copolymers with an alkoxysilane‐based core‐forming block: A comparison of synthetic approaches

Polymerization‐induced self‐assembly (PISA) has become the preferred method of preparing self‐assembled nano‐objects based on amphiphilic block copolymers. The PISA methodology has also been extended to the realization of colloidal nanocomposites, such as polymer–silica hybrid particles. In this work, we compare two methods to prepare nanoparticles based on self‐assembly of block copolymers bearing a core‐forming block with a reactive alkoxysilane moiety (3‐(trimethoxysilyl)propyl methacrylate, MPS), namely (i) RAFT emulsion polymerization using a hydrophilic macroRAFT agent and (ii) solution‐phase self‐assembly upon slow addition of a selective solvent. Emulsion polymerization under both ab initio and seeded conditions were studied, as well the use of different initiating systems. Effective and reproducible chain extension (and hence PISA) of MPS via thermally initiated RAFT emulsion polymerization was compromised due to the hydrolysis and polycondensation of MPS occurring under the reaction conditions employed. A more successful approach to block copolymer self‐assembly was achieved via polymerization in a good solvent for both blocks (1,4‐dioxane) followed by the slow addition of water, yielding spherical nanoparticles that increased in size as the length of the solvophobic block was increased. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2018 , 56, 420–429     

Synthesis of silanol-functionalized latex nanoparticles through miniemulsion copolymerization of styrene and gamma-methacryloxypropyltrimethoxysilane

The polystyrene latex nanoparticles bearing silanol groups on their surfaces were successfully synthesized via miniemulsion polymerization using gamma-methacryloxypropyltrimethoxysilane (MPS) as the functional comonomer and oil-soluble AIBN as the initiator at neutral conditions. FTIR and 29Si NMR spectra showed that the condensation of silanol groups was suppressed effectively. zeta potential and XPS analyses demonstrated that the silanol groups were enriched at the surfaces of the latex particles and could be tailored by MPS concentration. These silanol-functionalized latex particles could be easily coated with silica or other inorganic or organic compounds to prepare novel hybrid particles and hollow microspheres.     

甲基丙烯酸3-三甲氧基硅丙酯在乳液体系中的分配

通过气相色谱(GC)研究了甲基丙烯酸3_三甲氧基硅丙酯(MPS)在乳液体系各相中的分配行为,并测得了MPS在各种情况下的分配系数.发现当MPS加入量达到聚合物种子的约10 wt%时,体系进入饱和状态,且大部分MPS分配在粒子相中.通过对单体相分配行为的理论分析,并结合实验数据,发现种子乳胶粒粒径、聚合物种子中的化学组成对MPS的分配行为影响很小,而温度则使MPS在各相中的饱和浓度增加.     

New route to 3-methacryloxypropyltrimethoxysilane-base organic–inorganic hybrid film

A series of poly(3-methacryloxypropyltrimethoxysilane)/waterborne polyurethane (PMPS/WPU) composite latexes and organic–inorganic hybrid films with PMPS contents of 0, 10, 20, 30, 40 and 50 wt.% were prepared via seeded emulsion polymerization initiated by AIBN and hydrolysis–condensation process of PMPS during the evaporation of water, respectively. WPU, that is anionic polyurethane emulsion, was synthesized using isophorone diisocyanate, polytetramethylene ether glycol, dimethylol propionic acid, 1,4-butanediol, and triethylamine. An investigation of transmission electron microscopy confirmed the core–shell morphology of the composite latex particle which was composed of a PMPS core and a polyurethane shell. A dynamic light scattering analysis showed that the average particle size distributed in the range of 42–134 nm. The proposed novel preparation method included the use of polyurethane as macromolecular emulsifier and steric stabilizer, control of (3-methacryloxypropyltrimethoxysilane) (MPS) content less than 50 wt.%, slow addition of MPS and application of AIBN ensured the preparation of a stable PMPS/WPU composite latex. Formed PMPS/WPU organic–inorganic hybrid film with high PMPS content via sol-gel process had uniform transparency at visible band because of less crystalline and phase separation between organic and inorganic phases.     

Preparation of Silica/Poly(tert‐butylmethacrylate) Core/Shell Nanocomposite Latex Particles

Nanocomposite latex particles, with a silica nanoparticle as core and crosslinked poly(tert‐butylmethacrylate) as shell, were prepared in this work. Silica nanoparticles were first synthesized by a sol‐gel process, and then modified by 3‐(trimethoxysilyl)propyl methacrylate (MPS) to graft C?C groups on their surfaces. The MPS‐modified silica nanoparticles were characterized by elemental analysis, FTIR, and ²⁹Si NMR and ¹³C‐NMR spectroscopy; the results showed that the C?C groups were successfully grafted on the surface of the silica nanoparticles and the grafted substance was mostly the oligomer formed by the hydrolysis and condensation reaction of MPS. Silica/poly(tert‐butylmethacrylate) core/shell nanocomposite latex particles were prepared via seed emulsion polymerization using the MPS‐modified silica nanoparticle as seed, tert‐butylmethacrylate as monomer and ethyleneglycol dimethacrylate as crosslinker. Their core/shell nanocomposite structure and chemical composition were characterized by means of TEM and FTIR, respectively, and the results indicated that silica/poly(tert‐butylmethacrylate) core/shell nanocomposite latex particles were obtained.     

Anhydrous Sol-Gel Synthesis of Titania-Doped Siloxane Polymer for Integrated Optics

Sol-gel synthesis of organic-inorganic hybrid materials for planar waveguides and devices has received growing interest due to its low-cost processing and good suitability for doping. Titania is an important optical dopant, but homogeneous incorporation of titania in silica is difficult to be achieved by the conventional sol-gel process (aqueous system) because of the significant difference between the hydrolysis rates of the precursors. In this paper, we report an anhydrous sol-gel process for synthesising titania-doped siloxane polymers. The process consists of a hydrolysis of 3-methacryloxypropyltrimethoxysilane (MPS) with boric acid under anhydrous conditions, and a condensation with dimethyldimethoxysilane (DMDMS), diphenyldimethoxysilane (DPhDMS) and titanium ethoxide (TET). Optical characterisations for the produced titania-doped polymer were performed, and results showed that TET doping is useful for reducing the OH concentration of the synthesised polymer and is also effective for improving the optical quality of spin coatings. DMDMS and DPhDMS are favourable in reducing the birefringence and in increasing the thermostability of the material, and the methacryl groups of MPS are UV-polymerizable, which is useful for low cost fabrication of waveguides by photolithographic process. The results of ellipsometry scanning measurements show that titania is homogeneously incorporated in the hybrid matrix, suggesting that the anhydrous sol-gel process is useful for preparation of UV-sensitive titania-doped siloxane polymers for optical applications.     

Synthesis of Hybrid Hollow Sub‐microspheres Assisted by Pre‐added Colloidal SiO2

A novel method was developed to synthesize organic–inorganic hybrid hollow sub‐microspheres (HHSs) through the addition of colloidal SiO₂. The hydrolysis rate of 3‐(methacryloyloxy)propyltrimethoxysilane (MPS) was accelerated by SiO₂ particles; meanwhile, the condensation rate of the hydrolytic species was decelerated. Thus, the hydrolytic monomers and oligomers of MPS were preserved as emulsifiers. These emulsifiers can then emulsify the isopentyl acetate (PEA) to form a steady O/W emulsion. The HHSs were produced by subsequent free radical polymerization and removal of the oil core. The hydrolytic MPS acted as emulsifiers and polymerizable monomers at the emulsification and polymerization stage, respectively. Thus, extra emulsifiers, co‐emulsifiers, and organic monomers were omitted, which simplified the synthesis process. The good dispersion of HHSs in water and oil, as well as the EDX results, indicated the organic–inorganic hybrid structure of HHSs.     

Sol–gel technology as representative processing for nanomaterials: case studies on the starting solution

In order to fabricate sol–gel products with desired microstructure in the form of bulk, fiber and coating film, the appropriate selection of the composition of the starting solution is of primary importance. In this paper, the effects of the composition of the starting solution on the reaction in alkoxysilane solutions, the formation of bulk and fiber, and the microstructure of a particular coating film are reviewed, based on our experiences. It is shown in the alkoxysilane and alkylalkoxysilane solutions that, besides hydrolysis and random polymerization, various reactions take place. Among them, the formation of a four-membered ring molecule in dimethyldialkoxysilane solution, formation of a cage-like cubic octamer in an tetraalkoxysilane solution containing, for example, tetramethylammonium ion and stabilization of a solution for polycomponent oxides by the addition of tartaric acid are discussed. It is also shown that the composition of the starting solution suitable for fiber drawing is different from that for the formation of crack-free bulk gels: for the fiber drawing acid catalyst and low water content are required in various oxide systems including silica, while for the bulk silica gels ammonia-catalyzed alkoxysilane solution with dimethylformamide solvent or highly acidic solution works well for bulk silica gel. Finally, it is shown that the control of microstructure of coating films can be realized by selecting the composition of the starting solution. As an example, the change of the acid content of the starting solution produces three different microstructures of polycrystalline, crystal-oriented and amorphous structure in the lithium borate coating film. As another example, the size of precipitated noble metal particles in the coating film is controlled by the water and acid content of the solution. The mechanism of the above phenomena is also discussed.