Phase transition temperatures added polymers

To investigate the effect of adding monomeric and dimeric CD on the change of phase transition temperature of the polymers P18 and P19, we performed turbidity measurements at the same polymer concentration as above in the presence of a defined amount of Me-P-CD and CD dimer, respectively (Fig. 25 a,b) [61,62], As reported previously [56-59], we found that addition of Me-p-CD led to cloud points of polymers P18 and P19 of 32°C, which correlates to the LCST of pure poly(NIPAAM). This increase of the cloud points relative to the cloud points of pure P18 and P19 results from the inclusion of the hydrophobic adamantyl units by Me-P-CD. 

SI-IMP has been used for synthesis of different types of stimuli-responsive polymer brushes that are responsive to several external stimuli, such as pFI, temperature, and ionic strength [28,58-65]. Because materials interact with their surroundings via their interfaces, the ability to fashion soft interfacial layers and tune the range, extent, and type of physicochemical interactions across interfaces is central to a variety of applications. Rahane et al. carried out sequential SI-IMP of two monomers to create bilevel poly(methacrylic acid)-Woc/c-poly(N-isopropylacrylamide) (PMAA-b-PNIPAM) block copolymer brushes that can respond to multiple stimuli [28]. They observed that each strata in the bilevel PMAA-b-PNIPAM brush retained its customary responsive characteristics PMAA being a "weak" polyelectrolyte swells as pH is increased and the thermoresponsive PNIPAM block collapses as temperature is raised through the volume phase transition temperature due to its lower critical solution temperature (LCST) behavior. As a result of ions added to make buffer solutions of various pH and because of the effect of surface confinement, the swollen-collapse transition of the PNIPAM layer occurs at a... 

Though both miscible and immiscible blends are composite materials, their properties are very different. A miscible blend will exhibit a single glass transition temperature that is intermediate between those of the individual polymers. In addition, the physical properties of the blends will also exhibit this intermediate behavior. Immiscible blends, on the other hand, still contain discrete phases of both polymers. This means that they have two glass transition temperatures and that each represents one of the two components of the blend. (A caveat must be added here in that two materials that are immiscible with very small domain sizes will also show a single, intermediate value for Tg.) In addition, the physical properties... 

At present, we believe that the jump transitions observed in many of the gels studied here represent first order phase transitions. If this is the case, then the gels studied here are among the first found so far in which a first order phase transition occurs near room temperature in pure aqueous solvent with substantial added salt. Early studies by Tanaka s group with poly(acrylamide) based gels required that hydrophobic solvents such as acetone be added for a discontinuous phase transition to be observed near room temperature [6-10]. The more recently studied gels based on poly(n-isopropylacrylamide) [11, 12] and other lower critical solution temperature polymers show discrete phase transitions in water with no salt [11], but the swelling transitions become continuous when moderate amounts of salt are added [12],... 

The GC route is particularly attractive for it requires no a priori information on the polymer. With the exception of X-ray measurements, most methods of measurement involve a comparison of some property of the polymer, such as density, with that of the totally amorphous or crystalline material. Furthermore neither the mass of polymer in the column nor the flow rate of carrier gas need to be measured since a ratio of retention volumes is computed in Eq. (21). It should be added, however, ttiat for the successful application of the method it is essential that the measured retention volumes correspond effectively to equilibrium bulk sorption, both above and below. Low molecular weight compounds are known to exhibit apparently similar discontinuities in retention diagrams at their melting points but this is to be ascribed to a change in retention mechanism, from surface adsorption for the solid to bulk sorption for the liquid stationary phase. For a detailed discussion of retention characteristics of low molecular weight substances near their transition temperatures the reader is referred to a recent review by McCrea (8J). 

D. Patterson in 1968 based on an analysis of Flory-Rehner theory. It took ten years for the phenomenon to be experimentally observed after prediction. It was found by T. Tanaka that, when a critical amount of an organic solvent was added to a water-swollen poly(acrylamide) gel, the gel collapses. Many gels of synthetic and natural polymers have been studied. Subsequent experiments showed that a volume phase transition (swelling/collapse) could also be brought about by changes in other environmental parameters such as pH, ionic strength, and temperature. 

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