Thermal Properties of Particle Brush Materials: Effect of Polymer Graft Architecture on the Glass Transition Temperature in Polymer‐Grafted Colloidal Systems

Abstract

Summary:The governing parameters controlling the glass transition temperature of polymer-grafted particle systems are analyzed for the particular case of polystyrene (PS)-grafted silica colloids in the dense grafting limit. At a given degree of polymerization of surface-grafted chains the glass transition temperature is found to increase as compared to linear chain polymers of equivalent degree of polymerization. The difference in the glass transition temperature between polymer-grafted particle systems and their respective linear polymer analogs increases with decreasing degree of polymerization of surface-grafted chains and levels off at similar plateau values for particle brushes of distinct particle core size. The trend toward increased glass transition temperature is interpreted as a consequence of the increased steric hindrance in polymer-grafted particles that counteracts the relaxation of surface-grafted polymer chains. The increase in glass transition temperature is shown to be approximately consistent with the chain conformational regimes that are predicted on the basis of a Daoud-Cotton type scaling model.

Physical aging and glass transition of hairy nanoparticle assemblies

“…(B)]. This is similar to results shown by Dang et al Another possibility for the aHNP trends is a higher “effective” molecular weight of the polymeric canopy, since the chains are tethered to a common core. For example at graft densities of 0.6 chains/nm 2 , the number of chains per silica ( r o = 8 nm) is n = 480, and thus the total polymer molecular weight for the HNP canopy of short chains (10 kDa, aHNP‐PS‐18) easily approaches 10 3 kDa ( N = 4.8 × 10 4 ).…”

“…Alternatively, the reduction of the effective T g may be associated with constraints imposed on the packing of canopy chains due to tethering and space filling requirements. The scaling with silica volume fraction would then reflect an increasing fraction of PS chains with extended chain conformations as proposed by Dang et al As silica volume fraction increases at constant HNP σ , the brush architecture changes from SDP/CPB to CPB [Fig. (b)].…”

“…Additionally, the T g for the lowest silica content aHNP (aHNP‐PS‐1) is offset, outside experimental error, toward higher temperatures from the comparably filled, as well as unfilled, linear matrix. These observations (decreasing T g with silica content and higher T g relative to an equivalent linear matrix) are consistent with a recent report …”

Grafting of trifluoromethylated poly(phenylene oxide)s on a single‐walled carbon nanotube via surface‐initiated chain‐growth condensation polymerization

“…These variations may be attributed to the reduced conformational degree of freedom and the reduced number of chain ends resulting from the binding of the polymer chain end to the SWNT. The absence of melt crystallization of SWNT‐PPO compared to the complex melt crystallization behavior of CF 3 ‐PPO at 140 and 175–225 °C (Supporting Information, Fig. S2) provided further confirmation of chain grafting.…”

Effect of Molecular Architecture on Conformational Relaxation of Polymer Chains at Interfaces

“…[ 50,51 ] This scenario was also supported by a recent result evidencing an elevated glass transition temperature for polymer chains grafted onto silica nanoparticles though in this case, the depressed chain mobility was explained in terms of the stretching conformation of tethered chains in addition to the interfacial effect. [ 52,53 ] Postulating that the interaction between chains and the interface alters the chain dynamics at the interface, [ 10,54,55 ] the slower conformational relaxation for sPS could be understood. Also, if that is the case, the adsorption behavior of chains onto the substrate surface should be dependent on the architecture.…”