TY - JOUR
T1 - Accelerated brush growth on nanoparticle surfaces by reversible addition-fragmentation chain transfer polymerization
AU - Jiao, Yang
AU - Akcora, Pinar
PY - 2014/6/15
Y1 - 2014/6/15
N2 - It is now well established that controlling the grafted chain lengths and densities on nanoparticle surfaces determines the effective interactions between particles, and their assembly. Here, we present unusual kinetic results for achieving grafted chain lengths longer than the free chains using reversible addition-fragmentation chain transfer (RAFT) polymerization and discuss the limitations to obtaining polymer grafting density higher than ∼0.06 chains/nm2. We observe that surface initiated polymerization grows faster than the free chains in solution with high RAFT agent coverage (1.95 agents/nm2) on nanoparticles. The time-dependence of graft density suggests that activation of the anchored chain transfer agent (CTA) is limited by the diffusion of macro-radicals within growing grafts. Thus, radical transfer and exchange reactions become inefficient between grafts and free polymer, and convert the surface-initiated RAFT mechanism to a free radical polymerization.
AB - It is now well established that controlling the grafted chain lengths and densities on nanoparticle surfaces determines the effective interactions between particles, and their assembly. Here, we present unusual kinetic results for achieving grafted chain lengths longer than the free chains using reversible addition-fragmentation chain transfer (RAFT) polymerization and discuss the limitations to obtaining polymer grafting density higher than ∼0.06 chains/nm2. We observe that surface initiated polymerization grows faster than the free chains in solution with high RAFT agent coverage (1.95 agents/nm2) on nanoparticles. The time-dependence of graft density suggests that activation of the anchored chain transfer agent (CTA) is limited by the diffusion of macro-radicals within growing grafts. Thus, radical transfer and exchange reactions become inefficient between grafts and free polymer, and convert the surface-initiated RAFT mechanism to a free radical polymerization.
KW - diffusion-limited activation
KW - grafted particles
KW - grafting density
KW - growth
KW - iron oxide
KW - kinetics (polym.)
KW - polymer nanocomposites
KW - polystyrene
KW - reversible addition fragmentation chain transfer (RAFT)
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U2 - 10.1002/pola.27170
DO - 10.1002/pola.27170
M3 - Article
AN - SCOPUS:84900020101
SN - 0887-624X
VL - 52
SP - 1700
EP - 1705
JO - Journal of Polymer Science Part A: Polymer Chemistry
JF - Journal of Polymer Science Part A: Polymer Chemistry
IS - 12
ER -