Composition of block copolymers

The composition of block copolymers and, in particular, alternation of PAN and PEO blocks in the macromolecule of copolymers depends on the ratio between PEO and acrylonitrile in the reaction system. At low PEO concentrations in the reaction mixture a tri-block copolymer is probably formed with the following alternation of blocks ... 

In the absence of substantial unsaturation and of active groups on the chain for either polymer, only linear block copolymers are formed, according to the initiation Reactions 1 and 4. Low density polyethylene and high molecular weight polyisobutylene are typical of polymers which form block copolymer fractions on intensive mechanical working. The composition of block copolymers is related also to the relative rates of reaction, (Reactions 2 and 3) which is determined by the relative radical reactivity. 

In coi itrast, in living polymerization systems, the polymerization occurs without chain transfer or chain termination, giving greater control over polydispersity of the resultant polymers. Such polymerization systems allow the controlled synthesis of water-soluble polymers and enable precise control over the composition of block copolymers. 

As already shown above in Section 4.7, the composition of block copolymers can be changed in a systematic manner. Stupp and co-workers [36] have used this flexibility to investigate the ability of thin films of such materials to form... 

In general, a block copolymer added to immiscible polymer blend significantly suppresses the growth rate of phase-separated domains due to the reduction of interfacial tension resulting from a preferential localization of block copolymer at the interface. However, the retardation effect by the block copolymer is found to be dependent upon the structure of the block copolymer added, such as the interaction energy, the chain length, and the composition of block copolymer. 

The dependence of morphological features on the composition of block copolymers is summarized in Table IV. 

Table 8. Compositions of block copolymers determined by pyrol gas chromatography ...

Table 6B. Comparison of Compositions of Block Copolymers determined by various Methods ...

Composition of block copolymers The content of polypeptide (A-component) in each copol3nner, as represented by A mol-%, was determined from elemental analysis. The elemental analyses were carried out in the Organic Microanalyses Center in Kyoto University. As the molecular weight of the middle block is known, the molecular weight of the outer block, polypeptide block, is estimated from the copolymer composition. The molecular weight thus obtained is the number-average molecular weight. 

While contact angle measurements provided clearly some indication of the immediate surface composition of block copolymer membranes, provided solvent standards are available for direct comparison, ESCA offers the possibility of obtaining quantitative information on compositions, structures, and bondings in not only the immediate surface but also the subsurface typically to a depth of A (26, 27). 

Fig. 5.34 Plot of melting temperature against composition of block copolymers of poly(hexamethylene sebacate), HMS, with its isomer poly(2-methyl-2-ethyl-l,3-propylene sebacate), or with poly(dimethyl siloxane) O. (From O Malley (214))...

Indeed, PEG-PAsp(Dox) formed polymeric micelles with a diameter of 15 to 60 nm, which depended on the composition of block copolymers and dmg The dissociation rate of PEG-PAsp(Dox) micelles into... 

Del Rfo, R. Armijo, F Schrebler, R. Gutierrez, C. Amaro, A. Biaggio, S. R. Modification of composites of block copolymers-gold nanoparticles with enzymes and their characterization by electrochemical techniques. J. Solid State Electrochem. 2011, 15, 697-702. 

In principle, a determination of the mass allows for a measurement of the unique composition of block copolymers. It has been possible to determine the molecular weights and molecular weight distributions of both components of a block copolymer of polystyrene-WocA -poly(a-methylstyrene) by using MALDI-TOF [58]. The MALDI/TOF mass spectrum of a block copolymer sample containing 69% styrene and 31% a-methylstyrene is shown in Fig. 10.15. 

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