(399d) 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