Enthalpy and Volume Relaxation of Core‐Crosslinked Star Polystyrene/Poly(methyl methacrylate) Blends

Abstract

Blends of linear and core‐crosslinked star (CCS) polymers are prepared. The relaxation and thermal properties of the blends are determined using conventional and modulated‐temperature DSC and modulated‐temperature thermomechanometry. Addition of CCS polymers increase the glass transition temperature while decreasing the enthalpy and the linear coefficient of thermal expansion, suggesting that the hyperbranched polymers restrict matrix chain motions. Isothermal annealing increased the Tg and ΔH and decreased sub‐Tg α due to the reduced free volume and mobility within the polymer films. Volume relaxation during annealing is observed using mT‐TM, while a stretched‐exponential function is utilised to interpret the data. magnified image

Physical aging in polymers and polymer nanocomposites: recent results and open questions

“…The former kind of study delivers information on the thermodynamic state of the glass during physical aging. The most common recovery experiments are those involving the volume [10][11][12][13][14][15][16][17][18] and the enthalpy. 6,13,14,[16][17][18][19][20][21][22][23][24][25][26][27][28][29][30][31][32] Apart from the volume and enthalpy, a wide range of properties somehow related to thermodynamic ones have been recently monitored.…”

“…The most common recovery experiments are those involving the volume [10][11][12][13][14][15][16][17][18] and the enthalpy. 6,13,14,[16][17][18][19][20][21][22][23][24][25][26][27][28][29][30][31][32] Apart from the volume and enthalpy, a wide range of properties somehow related to thermodynamic ones have been recently monitored. Among them we can include measurements of the refractive index, [33][34][35] gas permeability, [36][37][38][39][40][41][42][43][44] dielectric related properties, 8,45-58 positron annihilation lifetime spectroscopy (PALS), [59][60][61][62][63][64] uorescent spectroscopy, [65]…”

Physical Aging of Polymer Blends

“…These include the modulatedtemperature-thermomechanometry technique (mT-TM) which has been recently employed to investigate blends of core cross-linked (CCS) PS and PMMA (Spoljaric et al 2011) and nanomechanical thermal analysis. By using silicon microcantilever deflection measurements, the latter technique can provide a measure of temperature-dependent thermal stresses and therefore investigate the influence of physical aging (Yun et al 2011).…”

Thermotropic dynamic processes in multiphase polymer systems by (cryo-)AFM

“…from the entire polymer bulk. [12][13][14][15][16][17][18][19][20] Therefore, in two chemically identical compositions different values may arise. 20 The clue lies in the recognition that the values of volume recovery and mechanical characteristics are specic for each polymer system (e.g.…”

“…[12][13][14][15][16][17][18][19][20] Therefore, in two chemically identical compositions different values may arise. 20 The clue lies in the recognition that the values of volume recovery and mechanical characteristics are specic for each polymer system (e.g. depending on temperature history, relaxation kinetics, and the instantaneous structure of the material) including interphase layers within the polymer blend bulk.…”