10.1021/acs.macromol.9b00810.s001
Che-Yi Chu
Che-Yi
Chu
Yen-Cheng Li
Yen-Cheng
Li
Guang-Way Jang
Guang-Way
Jang
Ying-Chih Pu
Ying-Chih
Pu
Meng-Zhe Chen
Meng-Zhe
Chen
Pei-Yin Chen
Pei-Yin
Chen
Qualitative Effect of the Polymerization Rate on the
Nanoparticle Dispersion in Poly(methyl methacrylate)/Silica Nanocomposite
Films
American Chemical Society
2019
particle surface
reactive vinyl groups
M-SiO 2
PMMA
large-length scale network structure
polymerization rate
MMA monomers
M-SiO 2 nanoparticles
2019-10-28 15:37:29
Journal contribution
https://acs.figshare.com/articles/journal_contribution/Qualitative_Effect_of_the_Polymerization_Rate_on_the_Nanoparticle_Dispersion_in_Poly_methyl_methacrylate_Silica_Nanocomposite_Films/10060154
In this study, we investigate the
effect of the polymerization
rate, mainly mediated by the initiator concentration, on the nanoparticle
dispersion in the nanocomposite films formed by poly(methyl methacrylate)
(PMMA) and [3-(methacryloyloxy)propyl]trimethoxysilane-modified silica
nanoparticles (M-SiO<sub>2</sub>) via free radical polymerization
of the precursory solution, that is, 15.5 wt % M-SiO<sub>2</sub> nanoparticles
dispersed in the methyl methacrylate (MMA) monomer, in which the tethered
silanes at the particle surface bearing the reactive vinyl groups
were capable of polymerizing with the MMA monomer. At slower polymerization,
the nanoparticles self-organized to form a large-length scale network
structure with the mass fractal of average dimension of 2.7; contrarily,
the nanoparticles exhibited better dispersion when the polymerization
proceeded at a faster rate. According to the scenario of perturbed
polymerization kinetics in the presence of nanoparticles, we propose
a possible mechanism through which the MMA monomers at a lower polymerization
rate may constitute longer “multiple grafted PMMA chains”
along particle surfaces by an optimal balance between the polymerization
of the monomer and the grafting reaction of the monomer onto the particle
surface, forming the M-SiO<sub>2</sub>-rich clusters by interparticle
bridging; the multiple grafting reaction also occurred in between
any two neighboring M-SiO<sub>2</sub> nanoparticles situated respectively
at the two adjoining clusters to induce the intercluster bridging,
thereby leading to a hierarchical fractal network. However, both the
polymerization and the grafting reaction of MMA monomers at a higher
polymerization rate formed the shorter free and grafted PMMA chains,
providing steric stabilization to retain better dispersity of nanoparticles.