Copolymers solution properties

Butadiene copolymers are mainly prepared to yield mbbers (see Styrene-butadiene rubber). Many commercially significant latex paints are based on styrene—butadiene copolymers (see Coatings Paint). In latex paint the weight ratio S B is usually 60 40 with high conversion. Most of the block copolymers prepared by anionic catalysts, eg, butyUithium, are also elastomers. However, some of these block copolymers are thermoplastic mbbers, which behave like cross-linked mbbers at room temperature but show regular thermoplastic flow at elevated temperatures (45,46). Diblock (styrene—butadiene (SB)) and triblock (styrene—butadiene—styrene (SBS)) copolymers are commercially available. Typically, they are blended with PS to achieve a desirable property, eg, improved clarity/flexibiHty (see Polymerblends) (46). These block copolymers represent a class of new and interesting polymeric materials (47,48). Of particular interest are their morphologies (49—52), solution properties (53,54), and mechanical behavior (55,56). 

Solubility and Solution Properties. Poly(vinyhdene chloride), like many high melting polymers, does not dissolve in most common solvents at ambient temperatures. Copolymers, particularly those of low crystallinity, are much more soluble. However, one of the outstanding characteristics of vinyUdene chloride polymers is resistance to a wide range of solvents and chemical reagents. The insolubiUty of PVDC results less from its... 

The dilute solution properties of copolymers are similar to those of the homopolymer. The intrinsic viscosity—molecular weight relationship for a VDC—AN copolymer (9 wt % AN) is [77] = 1.06 x 10 (83). The characteristic ratio is 8.8 for this copolymer. 

An extensive investigation of the dilute solution properties of several acrylate copolymers has been reported (80). The behavior is typical of flexible-backbone vinyl polymers. The length of the acrylate ester side chain has Httle effect on properties. 

An effective method of NVF chemical modification is graft copolymerization [34,35]. This reaction is initiated by free radicals of the cellulose molecule. The cellulose is treated with an aqueous solution with selected ions and is exposed to a high-energy radiation. Then, the cellulose molecule cracks and radicals are formed. Afterwards, the radical sites of the cellulose are treated with a suitable solution (compatible with the polymer matrix), for example vinyl monomer [35] acrylonitrile [34], methyl methacrylate [47], polystyrene [41]. The resulting copolymer possesses properties characteristic of both fibrous cellulose and grafted polymer. 

The observed anomaly in the viscous properties of dilute organotin copolymer solutions seems to be attributable to the existence of both intra- and intermolecular associates,due to coordination interactions between SnR3 and C=0 fragments of side groups. 

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... 

Several block and graft copolymers have been shown to form stable aggregates under thermodynamically poor solvent conditions, as a result of differences in the solubility of different parts of a macromolecule. Whereas in a good solvent the experimentally measured value of A2 for a copolymer represents the balance of all the multiple interactions, under thermodynamically poor conditions A2 is mainly determined by the interaction of the groups situated on the polymer-solvent interface. Groups which form the hydrophobic core and are not in a contact with the solvent do not contribute significantly to the solution properties of the copolymer. 

One such property, as has been demonstrated (see [26]), is the change in partial heat capacity of the copolymer solution upon the heat-induced conformational transition of macromolecules. Such a change was detected by high-sensitivity differential scanning calorimetry (HS-DCS). The DSC data for the NVCl/NVIAz-copolymers synthesized at initial comonomer ratios of 85 15 and 90 10 (mole/mole) are given as thermograms in Fig. 4. 

The transition enthalpies of the s- and p-fractions obtained from the feed with a comonomer molar ratio of 85 15 were equal to 6 and 7 J/g, respectively, i.e. the values are very close. This, therefore, can be indicative of almost the same average length of oligoNVCl blocks. Moreover, as we have already stressed, the fractions also had virtually the same final comonomer composition. However, since the solution properties of these fractions are drastically different, one can draw the conclusion that this is apparently due to a specific distribution of hydrophobic and hydrophilic residues along the polymer chains. In turn, because of all the properties that are exhibited by the s-fraction, this fraction can be considered to be a protein-like copolymer [27]. 

Solution prepregging, 20 284-285 Solution processing, 14 80 Solution process, of ethylene-propylene polymer manufacture, 10 708-710 Solution properties of lignin, 15 13 of polyampholytes, 20 479 ofVDC copolymers, 25 703-706 Solution spectrophotometry, 9 232 Solution spinning... 

Based on the solution property of poly (DMAEMA-co-AAm) in response to temperature, the temperature dependence of equilibrium swelling of poly (DMAEMA-c6>-AAm) gel as a function of chemical composition was observed as shown in Figure 6. The transition temperature of copolymer gel between the shrunken and swollen state was shifted to the lower temperature with increases in AAm content in the gel network. This is attributed to the hydrogen bond in the copolymer gel network and its hydrophobic contribution to the LCST Copolymer II gel was selected as a model polymer network for permeation study because it showed the sharp swelling transition around 34°C. 

Butun V, Vamvakaki M, BiUingham NC et al. (2000) Synthesis and aqueous solution properties of novel neutral/acidic block copolymers. Polymer 41 3173-3182... 

Namazi H, Adeli M. Solution properties of dendritic triazine/poly(ethylene glycol)/dendritic triazine block copolymers. J Polym Sci Part A Polym Chem 2005 43 28-41. 

As mentioned in Sect. 2.2.3, the biodistribution of HPMA copolymers depends on many factors. Molecular weight influences the uptake in the isolated tissue of yolk sac [266] as well as the elimination in vivo [124, 125,267,268]. Nonspecific increase in the rate of polymer uptake can be achieved by incorporation of positively charged or hydrophobic comonomers into the HPMA copolymer structure, such as methacryloyloxyethyltrimethylammonium chloride [22], N-methacryloyltyrosinamide [21], or N-[2-(4-hydroxyphenyl)ethyl]acrylamide [267]. The incorporation of hydrophobic moieties may influence the solution properties of the HPMA copolymer conjugates [132,134,269]. The interaction with the cellular surface may depend on the association number and the stability of the micelles. 

In fact, even in pure block copolymer (say, diblock copolymer) solutions the self-association behavior of blocks of each type leads to very useful microstructures (see Fig. 1.7), analogous to association colloids formed by short-chain surfactants. The optical, electrical, and mechanical properties of such composites can be significantly different from those of conventional polymer blends (usually simple spherical dispersions). Conventional blends are formed by quenching processes and result in coarse composites in contrast, the above materials result from equilibrium structures and reversible phase transitions and therefore could lead to smart materials capable of responding to suitable external stimuli. 

Therefore, polyrotaxanes can be simply defined as polymeric materials containing rotaxane units. They are different from conventional linear homopolymers because they always consist of two components, a cyclic species mechanically attached to a linear species. They also differ from polymer blends as the individual species are interlocked together and from block copolymers since the two components are noncovalendy connected. Thus new phase behavior, mechanical properties, molecular shapes and sizes, and different solution properties are expected for polyrotaxanes. Their ultimate properties depend on the chemical compositions of the two components, their interaction and compatibility. This review is designed to summarize the syntheses of these novel polymers and their properties. 

An early review of micellization in block copolymers was presented by Tuzar and Kratochvfl (1976), and these authors have recently provided an excellent review of the literature up to 1992 (Tuzar and Kratochvfl 1993). Micellar properties of block copolymers were also reviewed by Price (1982). A discussion of micellization was included in the general reviews on block copolymers by Riess et al. (1985) and Brown et al. (1989). Excellent reviews focussed on the solution properties of a particular class of copolymer, i.e. copolymers of polyoxyethylene) with poly(oxypropylene) have been presented by Alexandridis and Hatton (1995) and by Chu (1995) and Chu and Zhou (1996). Micellization and micellar association in related poly(oxyethylene)/poly(oxybutylene) copolymers have been summarized by Booth et al (1997). 

In this chapter, the focus is largely on experimental and theoretical studies of micellization in a range of solutions of model block copolymers prepared by anionic polymerization. A discussion of both neutral and ionic block copolymers is included, and features specific to the latter type are detailed. The adsorption of block copolymers at the liquid interface is also considered in this chapter. Recent experiments on copolymer monolayers absorbed at liquid-air and liquid-liquid interfaces are summarized, and recent observations of surface micelles outlined. Thus this chapter is concerned both with bulk micellization and the surface properties of dilute copolymer solutions. 

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