Low critical solution temperature

Properties. Hydroxypropylcellulose [9004-64-2] (HPC) is a thermoplastic, nonionic cellulose ether that is soluble in water and in many organic solvents. HPC combines organic solvent solubiUty, thermoplasticity, and surface activity with the aqueous thickening and stabilising properties characteristic of other water-soluble ceUulosic polymers described herein. Like the methylceUuloses, HPC exhibits a low critical solution temperature in water. 

The reaction may be conducted in stirred autoclaves in the presence of hydrocarbon diluents (82,83). Like the methylceUuloses, advantage is taken of the low critical solution temperature of HPC and it is purified through multiple washings with hot water. Consequendy, very low levels of residual salts and by-products are present in the final products. 

Acrylamide-V-isopropylacrylamide copolymer chromatogram, 257,258/ low critical solution temperature, 257,258/... 

In Fig. 3.3a and b, it was possible to observe the maximum value of ttc at the different temperatures that the monolayer can reach. At higher temperatures, rrc increases, PVP exhibits a low critical solution temperature (LCST) in water [45]. The PVP in 0.55 M aqueous Na2S04 exhibits a lower LCST at 301 K. For soluble amphiphilic monolayers, such as those of PVP, when the temperature is changed the loss of monolayer material must be considered due to the solubilization in the subphase. 

Yang, Xie, and Wu reported the syntheses of 2-ferrocenylethyl methacrylate, acrylate, methacrylamide, and acrylamide.231 Scheme 2.44 shows the preparation of the water-soluble polymer 167 by the copolymerization of 2-ferrocenylacrylamide with isopropylacrylamide. Depending on the ratio of organometallic-to-organic units the copolymer possessed low critical solution temperatures (LCST) of 26-29°C. Comparatively the pure organic poly(lV-iso-propylacrylamide) possessed an LCST of 32°C. 

If the temperature rises above another incompatibihty area may appear. Such an area has been observed in some polymer-solvent systems, which are characterized by a low critical solution temperature, LCST, T2c- In Figure 6.1, LCST is higher n UCST. The negative dependence of polymer-plasticizer compatibility on temperature suggests the theoretical probability that LCST also occurs in polymer-plasticizer systems such as PVC with either dii-sodecyl adipate, dibutyl phthalate, or tributyl phosphate. 

Thermoresponsive self-folding films can be designed using continuous thermal expansion, melting, shape-memory transition or polymers which demonstrate LCST (Low Critical Solution Temperature) behavior in solutions. Kalaitzidou et al. used continuous volume expansion with temperature and demonstrated thermoresponsive rolling-unrolling of polydimethylsiloxane-gold bilayers tubes at 60-70 °C [24a, 24b] which is due to different temperature expansion coefficients. 

A/-ISOpropyl Acrylamid6. Homopolymers from A(-isopropyl acrylamide (NlPAAm) are well known and have been of great interest because of their low critical solution temperature (LOST) behavior in water-solution. The polymer is soluble at low temperatures in water and precipitates above the LOST upon heating. Those kinds of polymers are potentially useful in the pharmaceutical or medical area. The homo- and copolymerization with water-soluble comonomers such as 2-hydroxyethyl methacrylate and characterization of the corresponding polymers of NlPAAm are described in some papers. In the case of copolymerization with hydrophobic comonomers, the use of an organic solvent is necessary, otherwise the polymerization has to be carried out in emulsion. But the different solubilities of the monomers in water often make the copol3unerization of water-soluble and water-insoluble monomers by classical emulsion polymerization difficult. Because of the above discussed property of cyclodextrin derivatives, these problems can be avoided if the copolymerization reactions are performed in the presence of cyclodextrin derivatives. 

While poly(ethylene oxide) (PEO) has high hydrophilicity and biocompatibility, poly(A-isopropyl acrylamide) (PNIPAM) is a well-known thermosensitive polymer having a low critical solution temperature in water at 32° C. Block copolymers containing PEO and PNIPAM are therefore expected to... 

The organometallic copolymer of ferrocenylethylacrylamide and isopropy-lacrylamide was prepared and was foimd to be soluble in water due to the minimal incorporation of the organometallic monomer. These polymers exhibited low critical solution temperatures (LCSTs) ranging from 26-29°C when compared to the LCST of 32°C for poly(A -isopropylacrylamide)." ... 

Figure 3.3 Phase diagram of a binary symmetric polymer blend with low critical solution temperature.

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