Side chain, molecular weights

Table 9.2 Characterization results for two series of arborescent polystyrenes with different side chain molecular weights (adapted from ref. 4)...

Recently the study of the dilute solution behavior of polymacromonomer, a limiting case of graft copolymer where each repeat unit carries a grafted chain, has been initiated. The main interests are focused on the dependence of conformation and size of the whole molecule on factors such as nature of the backbone and side chain, molecular weight of backbone and grafts, solvent interactions with respect to both components, and chain stiffness induced on the backbone due to the high grafting density and its dependence on the aforementioned factors [310-313]. 

Some studies dealing with the solid state properties of graft copolymers with liquid-crystal side chains have appeared in the literature [353-355]. The main attention is focused on the influence of molecular parameters (nature of the backbone and the side chains, molecular weight, etc.) on the mesomorphic properties of the liquid-crystal side chain. Salt complexes of PEO grafted onto various backbones were also considered [356] and the influence of the nature of thebackbone and salts on the conductivity of the resulting materials was studied. 

Control over the side-chain molecular weight was achieved through the amount of monomer added to the activated substrates. The B values obtained ranged from 1.1 to 1.3 for molecular weights (M ) reaching 7 X 10 g/mol. The same technique was also used to synthesize arborescent copolymers, by adding other monomers in the last side-chain growth cycle, namely, arborescent polystyrene- -poly(fert-butyl methacrylate) and polystyrene- -[polystyrene-fe-poly(2-vinylpyridine)] copolymers [115]. 

Bottlebrush polymers contain a long flexible macromolecule as a backbone to which side chains, which may also be flexible, are grafted [59, 60]. The idea then is that via suitable choices of parameters such as the grafting density, solvent quality, and side chain molecular weight the local stiffness of this cylindrical molecular brush can be controlled. The qualitative pictine one draws is that of a wormlike... 

For comparison purposes, a PLL(20)-g[3.0]-PEG(5) copolymer with PEG(5) side chains (molecular weight, 5 kDa) grafted onto a PLL(20) backbone at the grafting ratio of g[3.0], provided by SuSoS AG (Dtlbendorf, Switzerland), has also been employed. ... 

Arborescent homopolymers are interesting, among others, as model compounds to study the properties of branched macromolecules beyond other systems such as star-branched polymers and microgels, due to their high branching functionalities and the extensive control achieved over the architecture (branching density, side-chain molecular weight) of the molecules. The synthesis of arborescent styrene homopolymers and some of their physical properties will be discussed first. 

In this chapter, the properties of a series of poly(dimethylsiloxane-co-methylalkylsiloxane) (PDM-PMAS) of various alkyl side-chain lengths are discussed. These polymers contain 3.5 mol % methylalkylsiloxane units and are prepared from the same precursor thus, any effects due to variations in the percentage of alkyl substitution and main-chain molecular weight differences and effects due to block distribution of the alkyl substituents are eliminated. 

This observation that the length of the hydrocarbon chain could be varied from 16 to 26 carbon atoms without affecting the limiting area could only mean that at this point the molecules were oriented vertically. From the molecular weight and density of palmitic acid, one computes a molecular volume of 495 A a molecule occupying only 21 A on the surface could then be about 4.5 A on the side but must be about 23 A long. In this way one begins to obtain information about the shape and orientation as well as the size of molecules. 

Hydrogenation of polybutadiene converts both cis and trans isomers to the same linear structure and vinyl groups to ethyl branches. A polybutadiene sample of molecular weight 168,000 was found by infrared spectroscopy to contain double bonds consisting of 47.2% cis, 44.9% trans, and 7.9% vinyl. After hydrogenation, what is the average number of backbone carbon atoms between ethyl side chains ... 

We must be careful in assessing the experimental results on the viscosity of branched polymers. If we compare two polymers of identical molecular weight, one branched and the other unbranched, it is possible that the branched one would show lower viscosity. Two considerations enter the picture here. First, since the side chains contribute to the molecular weight, the backbone chain... 

StmcturaHy, guar gum comprises a straight chain of D-mannose with a D-galactose side chain on approximately every other mannose unit the ratio of mannose to galactose is 2 1 (53). Guar gum has a molecular weight on the order of 220,000 (54). 

Liquid crystal polymers are also used in electrooptic displays. Side-chain polymers are quite suitable for this purpose, but usually involve much larger elastic and viscous constants, which slow the response of the device (33). The chiral smectic C phase is perhaps best suited for a polymer field effect device. The abiHty to attach dichroic or fluorescent dyes as a proportion of the side groups opens the door to appHcations not easily achieved with low molecular weight Hquid crystals. Polymers with smectic phases have also been used to create laser writable devices (30). The laser can address areas a few micrometers wide, changing a clear state to a strong scattering state or vice versa. Future uses of Hquid crystal polymers may include data storage devices. Polymers with nonlinear optical properties may also become important for device appHcations. 

The name naphthenic acid is derived from the early discovery of monobasic carboxyUc acids in petroleum, with these acids being based on a saturated single-ring stmcture. The low molecular weight naphthenic acids contain alkylated cyclopentane carboxyUc acids, with smaller amounts of cyclohexane derivatives occurring. The carboxyl group is usually attached to a side chain rather than direcdy attached to the cycloalkane. The simplest naphthenic acid is cyclopentane acetic acid [1123-00-8] (1, n = 1). 

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