正反向同时引发ATRP制备凹凸棒土/聚苯乙烯杂化粒子

通过脱醇法在凹凸棒土（ATP）表面接枝γ-氨丙基三乙氧基硅烷（APTES）实现氨基化（ATP-APTES），再经酰胺化反应接枝α-溴代异丁酰溴，从而在ATP表面固载ATRP引发基团（ATP-Br）；最后以2，2-偶氮二异丁腈（AIBN）和ATP-Br为双组分引发体系进行正反向同时引发原子转移自由基聚合（SR&NI ATRP）制备ATP接枝聚苯乙烯杂化粒子（ATP@PS）。结果表明AIBN结合ATP-Br引发体系进行SR&NI ATRP具有活性/可控聚合的特征，随催化剂用量增大，体系过早偏离一级动力学行为。聚合温度在80℃，投料比为单体/催化剂/AIBN/ATP-Br=200/0.3/0.05/0.5的条件下，接枝聚合物和游离聚合物分子量差异随转化率（c）增大逐渐增加，转化率为31.1%时，两者分子量分布（PDI）均保持在1.54以下，ATP-Br表面ATRP引发基团的引发效率为6.3%。杂化粒子在PS基体中分散得到明显改善。

Preparation of attapulgite/polystyrene hybrid particles via simultaneous reverse and normal initiation atom transfer radical polymerization

Attapulgite (ATP) hybrid particles were prepared via a simultaneous reverse and normal initiation atom transfer radical polymerization (SR&NI ATRP). ATP was first activated with hydrochloric acid to enhance the surface reactivity, and γ-aminopropyltriethoxysilane (APTES) was chemically bounded on the surface of ATP (ATP-APTES) via dealcoholization reaction. Then, ATP with ATRP initiating groups (ATP-Br) was prepared by amidation reaction between ATP-APTES and α-bromoisobutyryl bromide. Finally, SR&NI ATRP of styrene was conducted using copper bromide (CuBr₂) complex tris(2-(dimethylamino)ethyl)amine (Me₆-TREN) as the highly active catalytic system, initiated by 2,2-azobis(isobutyronitrile) (AIBN) and ATP-Br as a dual-component initiation system, and hybrid ATP particles grafted with polystyrene (ATP@PS) was obtained. The whole procedure was traced by gas chromatography (GC), Fourier transform infrared spectroscopy (FTIR), thermo gravimetric analysis (TGA), and X-ray photoelectron electron microscopy (TEM) in detail. The effects of different molar ratio of catalyst on the first-order kinetic behavior were investigated. The experimental results showed that polymerization of styrene under the AIBN-α-bromo amide initiation system and CuBr₂/Me₆-TREN catalyst displayed the living/controlled nature. As the increase of molar ratio of catalyst, the polymerization was deviated from the first-order kinetic prematurely, and the initiating efficiency was enhanced. When polymerization was performed at 80℃ under the ratio value of St]/CuBr₂/Me₆-TREN]/AIBN]/ATP-Br]=200/0.3/0.05/0.5, both of the molecular weight of grafted and free PS were grown in a controlled manner with a lower PDI (<1.54), and the difference of them was increased with conversion increasing. When proceeded SR&NI ATRP with 31.1% monomer conversion, the initiating efficiency was calculated to be 6.3%, and about 1.4 g·g^-1 grafting ratio of hybrid particles was achieved. The thickness of grafted layer was attained to about 14 nm. Simultaneously, inhomogeneous distribution was observed, which resulted from the coupling termination between the surface-anchored and free active sites. The dispersion property of ATP@PS in PS matrix was improved obviously.