Negative temperature-sensitive polymers

Negatively, temperature-sensitive hydrogels possess a LCST and contract upon heating above the LCST. This type of swelling behavior is known as the inverse (or negative) temperature dependence. Inverse temperature-dependent hydrogels are comprised of polymer chains which either possess moderately hydrophobic groups or a mixture of hydrophilic... 

Another class of thermally stable materials with electroactivity are polyacene quinone radical (PAQR) polymers. The thermal stability of PAQR polymers was. studied up to 1200°C under helium. The electrical conductivity was found to go through a minimum at about 500"C, showing that the original synthetic structure of a PAQR polymer is unique and thermally sensitive and that the negative temperature dependence of e.c. makes it similar to degenerate semi-metals [237]. 

The development of active ceramic-polymer composites was undertaken for underwater hydrophones having hydrostatic piezoelectric coefficients larger than those of the commonly used lead zirconate titanate (PZT) ceramics (60—70). It has been demonstrated that certain composite hydrophone materials are two to three orders of magnitude more sensitive than PZT ceramics while satisfying such other requirements as pressure dependency of sensitivity. The idea of composite ferroelectrics has been extended to other appHcations such as ultrasonic transducers for acoustic imaging, thermistors having both negative and positive temperature coefficients of resistance, and active sound absorbers. 

Steric Stabilization. Steric stabilization was a term first introduced by Heller to explain how adsorbed polyethylene oxide polymers increased the salt concentration required for flocculation of negatively charged aqueous suspensions.(6) Heller s systems were stabilized by both mechanisms, as are most commercial dispersions today, aqueous and non-aqueous. Much of the more recent literature on steric stabilizers has been preoccupied with solubility requirements, for the solubility of polymers is a delicate matter and very sensitive to temperature and solvent... 

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