Motion near the Glass Transition

A piece of polystyrene is placed under 100 atm pressure at room temperature. What is the fractional volume decrease  

What is the free volume of polystyrene at 100°C What experimental or theoretical evidence supports your conclusion  

A rubber ball is dropped from a height of 1 yard and bounces back 18 in. Assuming a perfectly elastic floor, approximately how much did the ball heat up The heat capacity, Q, of SBR rubber is about 1.83 kJ kg -K  

Write a 100- to 125-word essay on the importance of free volume in polymer science. This essay is to be accompanied by at least one figure, construction, or equation illustrating your thought train. 

A new polymer was found to soften at 50°C. Several experiments were performed to determine if the softening was a glass transition or a melting point. 

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APPENDIX 8.1 MOLECULAR MOTION NEAR THE GLASS TRANSITION... 

The Polymer-Surface Interaction. When using a nitroxide labeled polymer the polymer-surface interaction in the absence of solvent can be assessed from temperature studies in the presence and absence of the surface, as shown in Figures 9 and 10. At temperatures below or near the glass transition the effect of the surface cannot be deduced as all motions are too slow. However, as the temperature is raised above T the effect of the surface is clearly discernible, with surface inhibiting segmental motion. It is evident from Figures 9 and 10 that the absolute temperature is not as important as T-T, where T is the T in... 

The Adam-Gibbs eory can be corrected by assuming that a portion of the entropy A 5 measured calorimetrically does not couple to the glass transition and therefore remains finite at 7b thus Sc < AS (Miller 1978). The uncoupled entropy AS — Sc is presumably associated with motions that are not quenched at the glass transition. If this portion of A 5 is assumed to he insensitive to temperature near the glass transition and is assumed to be of... 

The current interest is the examination of the consequences of fiee-volume theory on the effect of the solvent size on diffusional behavior, and the behavior of the diffusion process near the glass transition. Clearly, these two problems are interrelated. The experimental data needed to investigate both are accurate diffu-sivity-temperature data for a series of solvents that covers a wide range of molecular sizes. The series of solvents used should include solvents of large molecular size, incapable of segmental motion. Some recent work is reported hoe using polymethyl methacrylate, an amorphous polymer that can be studied over a wide temperature range. 

In Chapter 7, Mano and Dionisio describe how electrical methods, and particularly dielectric relaxation spectroscopy (DRS) and thermally stimulated depolarisation current (TSDS) techniques, play a major role as tools for e2q)loring molecular mobility. DRS enables molecular relaxational processes (both slow and fast) to be studied. For example, the localized motions of glass formers in the glassy state give rise to local fluctuations of the dipole vector that are the origin of the secondary relaxation processes detected by dielectric relaxation spectroscopy, while above, but near, the glass transition, cooperative motions result in a distinguishably different relaxation process (the a-relaxation). 

Three reproducible transition processes were consistently observed. Near the glass transition temperature, subtle softening or smoothing occurred on the irregularly-shaped PS particles. Twitching motions were often noted for samples in this temperature range, presumably due to stress relaxation processes just above Tg. 

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