The Glass Transition Temperature of Polymer Melts†

2005 ◽  
Vol 109 (45) ◽  
pp. 21285-21292 ◽  
Author(s):  
Jacek Dudowicz ◽  
Karl F. Freed ◽  
Jack F. Douglas
Keyword(s):  
Glass Transition ◽  
Transition Temperature ◽  
Glass Transition Temperature ◽  
Polymer Melts

Glass transition of ion-containing polymer melts in bulk and thin films

Soft Matter ◽  
2021 ◽  
Vol 17 (37) ◽  
pp. 8420-8433 ◽  
Author(s):  
Wei Li ◽  
Monica Olvera de la Cruz
Keyword(s):  
Thin Films ◽  
Molecular Dynamics ◽  
Glass Transition ◽  
Transition Temperature ◽  
Glass Transition Temperature ◽  
Molecular Dynamics Simulations ◽  
Polymer Melts ◽  
Transition Behavior ◽  
Dynamics Simulations

We investigate the glass transition behavior of ion-containing polymers via molecular dynamics simulations, revealing its coupling with ionic correlations as well as variations of the glass transition temperature in bulk and thin films.

Effects of counterion size and backbone rigidity on the dynamics of ionic polymer melts and glasses

2017 ◽  
Vol 19 (40) ◽  
pp. 27442-27451 ◽  
Author(s):  
Yao Fu ◽  
Vera Bocharova ◽  
Mengze Ma ◽  
Alexei P. Sokolov ◽  
Bobby G. Sumpter ◽  
...  
Keyword(s):  
Dielectric Constant ◽  
Relaxation Time ◽  
Glass Transition ◽  
Transition Temperature ◽  
Glass Transition Temperature ◽  
Polymer Melts ◽  
Static Dielectric Constant ◽  
Segmental Dynamics ◽  
Ionic Polymer ◽  
Segmental Relaxation

Backbone rigidity, counterion size and the static dielectric constant affect the glass transition temperature, segmental relaxation time and decoupling between counterion and segmental dynamics in significant manners.

Rheological Properties of Polymers Modified with Carbon Dioxide

2004 ◽  
Author(s):  
Charles W. Manke ◽  
Esin Gulari
Keyword(s):  
Carbon Dioxide ◽  
Glass Transition ◽  
Transition Temperature ◽  
Glass Transition Temperature ◽  
Polymer Melts ◽  
Polymer Synthesis ◽  
Environmental Concerns ◽  
Melt Viscosity ◽  
Blowing Agents ◽  
Synthesis And Processing

Use of supercritical fluids (SCFs), particularly supercritical carbon dioxide, as alternative solvents in polymer synthesis and processing is a rapidly growing research area with successful industrial applications (McCoy, 1999). In some cases, the need for alternative solvents is based on environmental concerns, with regulations mandating replacement solvents. An environmentally mandated example is the 1995 ban of the use of chlorofluorocarbons (CFCs) as physical blowing agents in the manufacture of polymeric foams after CFCs were classified as class-I-ozone-depleting substances (ODPs). Among the alternative blowing agents are gases like CO2 and N2 and refrigerants such as 1,1-difluoroethane (R152a) and 1,1,1,2-tetrafluoroethane (R134a). Under the foaming conditions, at temperatures above the glass transition temperature of a polymer, and at pressures required for flow of highly viscous polymer melts, these alternative blowing agents are frequently supercritical. When polymers are formed into final products by various melt-processing techniques, such as extrusion, injection molding, blow molding, foaming, and spin-coating, extremely high melt viscosity presents a major difficulty. A common method to moderate the processing conditions is to add a liquid solvent or plasticizer to the melt. Solvents and plasticizers lower the glass transition temperature, Tg, of the polymer so that the polymer can be made to flow at lower pressures and temperatures. Replacing liquid solvents with SCFs presents unique processing advantages. Higher diffusivity and lower viscosity of SCFs, compared with liquid solvents, increase rates of dissolution and mixing. The properties of polymer–SCF solutions are tunable via pressure or temperature changes, thus allowing efficient downstream separations. Most importantly, dissolution of an SCF produces very large reductions in melt viscosity compared with a liquid solvent dissolved in the melt. Whether the interest in using SCFs in polymer synthesis and processing is driven by environmental concerns or processing advantages, it is important to understand the rheological behavior of polymer–SCF mixtures. In this chapter, we describe rheological measurements of polymer melts containing dissolved gases for two polymers, polydimethylsiloxane (PDMS) swollen with CO2 at 50 °C and 80 °C and polystyrene (PS) swollen with CO2, R152a, and R134a at 150 °C and 175 °C.

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