Within polymer physics and interfacial thermodynamics, the glass transition temperature characterizing the transition from elastomeric to glassy states is a parameter for evaluating thermal-mechanical stability. However, when polymer chains are infiltrated and confined within aerogel nanopores, surface adsorption from solid walls and geometric confinement induce shifts in glass transition temperatures. Analyzing glass transition temperature shifts and free volume physics in confined channels clarifies the dynamic mechanical behavior of constrained polymers.

In unconstrained macroscopic states, polymer glass transition relies on free volume to support cooperative segment rearrangements and rotational dynamics. Once polymers enter aerogel nanopores, segments near pore walls experience electrostatic adsorption and steric constraints, compressing local free volume and restricting chain mobility. This interfacial retardation effect propagates inward toward pore centers.

When aerogel surfaces exhibit strong attractive interactions, the effective glass transition temperature shifts toward higher temperatures; conversely, weak interfacial interactions induce negative shifts. This glass transition shift coincides with the broadening of relaxation time spectra and the reconstruction of local free volume distributions. Characterizing confined free volume evolution enables prediction of creep resistance in polymeric aerogels under thermal and mechanical loads.