Copolymer in water

The thermal expansion coefficients of PVCL and a copolymer in water, tfpol> were determined by PPC as a function of temperature (Fig. 23) [180]. The plots can be divided into four temperature ranges. Below the transition temperature, 10 < T < 30 °C, g i for PVCL remains constant, while in the case of PVCL-g-34, apoi has a negative slope. In both cases, apoi undergoes a sharp... 

The association of the graft copolymers in water at room temperature was studied by DLS [180]. The hydrodynamic radius of the various copolymers in dilute aqueous solutions at 20 °C, well below the cloud point, was determined for solutions ranging in concentration from 1 to 10 gL1. Similar measurements were also conducted for solutions of an unmodified PVCL of similar molecular weight (Fig. 24a). The hydrodynamic radius of PVCL is of the same order of magnitude in aqueous solution and in tetrahydofuran, a good sol-... 

Fig.24 Size distributions of PVCL and the graft copolymers in water at 20 °C. Homopolymer PVCL (a), grafted copolymers PVCL-g-13 (b), PVCL-g-18 (c), and PVCL-g-34 (d). Polymer concentration 10gL 1. (Reprinted with permission from Ref. [180] copyright 2005 Elsevier)...

The plots of h/h vs. copolymer concentration also reveal differences in the micropolarity of the hydrophobic domains created upon association of the various copolymers in water. A qualitative assessment of this property is given by the h/h value determined in the copolymer solutions of highest concentration when the plateau value is attained (Fig. 25). This value depended significantly on the grafting level the solution of the most densely grafted copolymer yielded the lowest h/h value (1.40) and the pure homopolymer the highest. In all cases, this value is higher than the value (1.20) recorded for micellar solutions of the macromonomer. It can be concluded... 

Fig. 9 Cryo-TEM picture of vesicles formed by the PMAA49-PDMAEMA11 ampholytic copolymer in water at pH = 9. Reprinted with permission from [174], Copyright (2000) American Chemical Society...

Core-shell-corona micelles were formed by PEHA-PMMA-PAA triblock copolymers in water, as demonstrated by Kriz et al. [266]. Ishizone et al. [267] synthesized ABC triblock copolymers containing 2-(perfluorobutyl)ethyl methacrylate, tBMA, and 2-(trimethylsilyloxy) ethyl methacrylate with various block sequences. These copolymers were converted into amphiphilic sys-... 

Fig.24 TEM picture of cylindrical micelles formed by a PFSi2-[Ru]-PEC>7o metallosupramolecular copolymer in water. No contrasting agent has been added for visualization of these micelles because they contain iron atoms in the core. Reprinted with permission from [331]. Copyright (2004) Wiley...

In principle, aqueous ATRP offers the tantalising possibility of the direct synthesis of reasonably well-defined zwitterionic block copolymers in water without recourse to protecting group chemistry. However, ATRP in acidic media is generally unprofitable, hence the (co)polymerisation of acidic monomers such as methacrylic acid or 4-vinylbenzoic acid must be carried out in weakly alkaline solution, i.e. the monomer should be in its anionic carboxylate... 

Lopes JR, Loh W. Investigation of self-assembly and micelle polarity for a wide range of ethylene oxide-propylene oxide-ethylene oxide block copolymers in water. Langmuir 1998 14 750-756. 

Water-soluble random copolymers containing L-serine and A/5-(4-hydroxybutyl)-L-glutamine are prepared, and the thermally induced helix-coil transition of these copolymers in water is studied. The Z/mm-Bragg parameters cr and s for the (hypothetical) helix-coil transition in poly(l-serine) in water are deduced. The values of s, computed from both the Lifson and Allegra theories are (.Llfson, o-1 x 10-4 / Allegra, o = 7.5 x 10 5 s - 0.667/0.726 (273 K), 0.757/0.784 (293 K), 0.777/0.792 (313 K), 0.731/0.744 (333 K),... 

The synthesis and characterization of water-soluble "random" copolymers containing t-valine with either A -O-hydroxypropyD-L-glutamine or / -(A-hydroxybutyD-L-glutamine are described, and the thermally induced helix-coil transitions of these copolymers in water are studied. The incorporation of /.-valine is found to decrease the helix content of the polymer at low temperatures and increase it at high temperatures. The Zimm-Bragg parameters o and s for the helix-coil transition in poly(t-valine) in water are deduced from an analysis of the melting curves of the copolymers. The values of s, computed for o = 1 x 1CI-4, are s 0.85 (273 K), 0.93 (293 K), 1.00 (313 K), 1.06 (333 Kl. 

In ionic block copolymers, micellization occurs in a solvent that is selective for one of the blocks, as for non-ionic block copolymers. However, the ionic character of the copolymer introduces a new parameter governing the structure and properties of micellar structures. In particular, the ionic strength plays an important role in the conformation of the copolymer, and the presence of a high charge density leads to some specific properties unique to ionic block copolymers. Many of the studies on ionic block copolymers have been undertaken with solvents selective for the ionic polyelectrolyte block, generally water or related solvents, such as water-methanol mixtures. However, it has been observed that it is often difficult to dissolve ionic hydrophilic-hydrophobic block copolymers in water. These dissolution problems are far more pronounced than for block copolymers in non-aqueous selective solvents, although they do not always reflect real insolubility. In many cases, dissolution can be achieved if a better solvent is used first and examples of the use of cosolvents are listed by Selb and Gallot (1985). 

With nonionic PEO emulsifiers, intermolecular interactions vary with temperature and types of metal ions and solvents. At low temperatures, nonionic emulsifiers are hydrophilic and form normal micelles. At higher temperatures they are lipophilic and form reverse micelles. A weak interaction with metal ions favors the stability of associates against moisture. On the other hand, a strong interaction may lead to a completely amorphous system. Ethanol as a co-solvent is a moderate solvent for PEO at low temperatures, but its power improves as the temperature is raised [34]. This means that solutions of the PEO copolymers in water and ethanol have opposing temperature coefficients of solubility negative for water and positive for ethanol. 

MACA as a hydrophobic comonomer can be used to modify PNIPAM. Copolymers, PNIPAM-co-MACA with different amounts of MACA can be synthesized by free-radical copolymerization of NIPAM and MACA in a mixture of methanol and chloroform with AIBN as the initiator. The resulting copolymers after purification can be dried in vacuum at 40 °C for 24 h. Hereafter, these copolymers are denoted as PNIPAM-co-x-MACA, where x denotes the molar percent of MACA. As expected, their solubility in water decreases as the MACA content or the solution temperature increases. It is also expected that the copolymer chains with a higher MACA content would have a lower LCST in comparison with PNIPAM homopolymer chains. In order to prepare a true solution, one has to dissolve these copolymers in water at low temperatures. The chemical structure of PNIPAM-co-MACA is as follows (Scheme 7). 

Fig. 7 Temperature dependence of partial heat capacity (Cp) of two pairs of NIPAM-co-VP copolymers in water. The weight average molar masses of NIPAM-co-VP/60/5, NIPAM-co-VP/30/5, NIPAM-co-VP/60/10 and NIPAM-co-VP/30/10 are 2.9 x 106, 4.2 x 106, 5.6 x 106 and 7.9 x 106 g/mol, respectively. The polymer concentration is 10-3 g/mL. The temperature was increased with a rate of 1.5 °C/min and pressure was maintained at 180 kPa [56]...

Fig. 26 Temperature dependence of partial heat capacity (Cp) of PNIPAM homopolymer, PNIPAM-co-St (4.1 mol %) random copolymer and NIPAM-seg-St (3.9 mol %) segmented copolymer in water the polymer concentration was 1.0 g/L and the heating rate was 0.5 °C/min. The inset shows the de-convolution of stand partial heat capacity (C ) of PNIPAM-seg-St [94]...

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