Polymer immersion

Gels are cross-linked networks of polymers immersed in a fluid medium. It is now well known that they can exhibit large volume changes in response to many different stimuli temperature, solvent composition, pH, electric fields. The universality of this volume phase transition of gels has now been clearly established. These stimuli-responsive gels have opened a new field of research by generating numerous experimental and theoretical works they also pave the way for a variety of new technologies (/). 

This technique clearly assumes that the polymer is not swollen appreciably by the liquid. Cate should be exercised to verify this fact using a dense thin-film sample of the polymer immersed in the candidate liquid. In addition, the apparent value of h 2, determined roughly as the difference between the centrifuged sample weight and the dry weight, should be corrected to account for actual molecular sorption into the polymer mass. This sorption, which occurs in addition to the capillary uptake, can produce an overestimation of the void volume percent in the fiber by as much as 5% if unaccounted for. The simplest means of accounting for such sorption involves adjustment of the value of Wj using sorption data for the liquid in the dense film for which capillary effects are not present. 

System composed of polymers or containing polymers immersed in low molecular media are extremely complex... 

The kinetics of release of the additive from the polymer immersed in the liquid, were determined by measuring the increase in concentration of the additive in the liquid by UV spectrometry. 

Some studies have indicated that the weight update curves for polymers immersed in different solvents show a decrease after reaching a maximum. This phenomenon is attributed to a leaching-out effect. In some polymeric systems, the presence of solvents produces an overshoot effect followed by a... 

Manual methods of freeze fracture are often useful in providing specimens for study in the SEM. An example of a freeze shattering method was described by Stoffer and Bone [406] for comparison with microtomy results. Polymers immersed in liquid nitrogen were mechanically shattered with a hammer, mounted, vacuum pumped and sputter coated for observation. This simple method is useful if the materials cannot be sectioned. However, fine structural details are not conclusive when specimens are prepared by such methods. 

An early version of the in vitro collagenase degradation assay was based on measurement of stress relaxation of a strip of test polymer immersed in a standardized collagenase bath. Previously, Tobolsky had used such a device to study the chemical stress relaxation of natural rubber in the presence of ozone. In spite of its immediate utility as a screening probe in our early research this experimental arrangement was eventually replaced by a more reproducible assay. The latter is an adaptation of a colorimetric procedure originally developed by Mandl and coworkers. ... 

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