The SEM Study and Molecular Dynamic Simulations of Nanosilica Grafted By Copolymer

The SEM Study and Molecular Dynamic Simulations of Nanosilica grafted by Copolymer

Shanshan Dai^a,b,*, Jinghan Zhang^a, Xiaowen Zhao^c

a. College of Chemistry and Chemical Engineering, Southwest Petroleum University, Chengdu 610500, Sichuan, China; b. Oil & gas Field Applied Chemistry Key Laboratory of Sichuan Province, Chengdu 610500, Sichuan, China; c. State Key Laboratory of Polymer Materials Engineering, Polymer Research Institute of Sichuan University, 610065 Chengdu, China.

Acryl amide (AM) acrylic acid (AA) copolymer grafting nanosilica were prepared by inverse microemulsion polymerization to make functional materials where nano-SiO₂ provides the rigidity and strength, and the copolymer the elasticity and flexibility. The resulting microspheres are able to enter, expand, shut off and remove in the deep-layers of oilfield. SEM photographs (Fig.1) proved the structure of core-shell, but lots of quantitative relationships are still missing. To solve this problem, molecular dynamic (MD) simulation is applied in this study and the modification of inorganic particle nanosilica becomes the first key point. There are 4 kinds of coupling agents. H1, H2, H3, and H4 represent the system with methyl-, octyl-, vinyl- and ¦Ã-methacryloxy propyl-triethoxysilane respectively. As shown in Fig. 2-4, H3 is the system with the highest binding energy between nanosilica and copolymer; Radius distribution function (RDF) supplies a measure of the probability that gives the presence of an atom at the origin of an arbitrary reference frame, and the higher value illustrates the bigger grafting density; Small slope value of the best-fit line of mean square displacement (MSD) curve indicates the bad mobility of copolymer chain, namely, the copolymer chains are fixed by modified SiO₂ surface.

*Correspondence to: Shanshan DAI (E-mail: ashanscu@163.com).

Grant Sponsor: National Natural Science Foundation of China (Grant Number: 51304163); China Postdoctoral Science Foundation (Grant Number: 2014M562507XB).

Fig. 1 The SEM of the core-shell microspheres

Fig. 2 The binding energy of systems with different coupling agent

Fig. 3 The RDF of systems with different coupling agent.

Fig. 4 The logMSDs of copolymer versus time in systems with different coupling agent