Chain length, and copolymer composition

The phase diagram of polyolefins and hydrocarbon diluents is exemplified for high-density polyethylene in Figure 1. When the polymer-diluent mixture is heated, dissolution of the semicrystalline polymer takes place along the borderline 1 (turbidity curve) [43, 44], This line depends on the polymer (e. g., polyethylene, isotactic polypropylene), average chain length, and copolymer composition. 

Controlled chain length and copolymer composition Figure 5.2 Various architectures that can be prepared with LRP. 

After investigating the effect of comonomer composition on the chain association as well as the effect of comonomer distribution on the chain folding, Siu et al. [141] extended their study to the effect of comonomer distribution on the chain association. They copolymerized NIPAM and vinyl pyrroli-done (VP) at temperatures, respectively, higher and lower than the LCST, which resulted in segmented and random VP distributions on the PNIPAM chain backbone. The synthesis characterization of these PNIPAM-co-VP amphiphilic copolymers with a similar chain length and comonomer composition, but different comonomer distributions, were described in previous sections. 

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 ATRP of the methacrylate monomers was performed at 60°C in ethanol solutions and in the presence of the catalyst copper(I) chloride/2,2 bipyridyl (Bipy) (Table 1, Entries 1-4). Copolymers P(ME02MA-co-OEGMA) of various chain-lengths and comonomer compositions were prepared and isolated in high yields. After purification, H NMR analysis confirmed that the formed polymers exhibit a terminal cholesterol moiety. Additionally, as previously demonstrated, the molar fraction of OEGMA in the copolymers was found, in all cases, to be almost equal to the fraction of OEGMA in the initial comonomer feed. Furthermore, SEC measurements in THF indicated that all the copolymers are rather well-defined (Table 1, Entries 1-4). 

Figure 5.14 Effect of radial concentration profiles on the chain length and chemical composition distributions of an ethylene/1-hexene copolymer (four microparticle layers were used for simplicity sake many more layers are required in an actual MGM simulation) [131],...

For the case of linear binary copolymers, the instantaneous bivariate chain length and chemical composition distribution, w(r, y), is described by Stockmayer s distribution [Eqs. (16)-(19)] [34]. 

These membranes are beneficial to separate CO2/H2 mixture as well. While conventional polyimides exhibited higher permeability for H2 than that of CO2, polyether-containing polyimides showed reverse selective characteristics. As increasing the chain length and molar composition in the block copolymer, CO2 permeability as well as CO2/H2 selectivity improved simultaneously. As highly condensable CO2 competed with H2 for the sorption sites in hard segment, mixed... 

Simulation of the (n-Bu)3SnH reduction of PVC is carried out in a manner similar to that described for TCH. Instead of beginning with 100 TCH molecules we take a 1000 repeat unit PVC chain that has been Monte Carlo generated to reproduce the stereosequence composition of the experimental sample of PVC used in the reduction to E-V copolymers (2), ie. a Bernoullian PVC with P =0.45. At this point we have generated a PVC chain with a chain length and a stereochemical structure that matches our experimental starting sample of PVC. 

In the SEC mode, the separation occurs according to the molecular size of a macromolecule in solution, which is dependent on its chain length, chemical composition, solvent, and temperature. Thus, molecules of the same chain length but different composition may have different molecular sizes (hydrodynamic volumes). Since SEC separates according to hydrodynamic volume, SEC in different eluents can separate a copolymer in two diverging directions. This principle of... 

We have a specific interest in the self-assembled structures formed by poly(ferrocenylsilane) block copolymers, such as poly(ferrocenyldimethylsilane-Z -dimethyl-siloxane) (PFS-PDMS) and (ferrocenyldimethylsilane-Z>-isoprene) (PFS-PI). The PFS block contains an iron atom in the main chain repeat unit. These polymers are particularly promising for novel applications, since they can be used as charge-transport materials and, by pyrolysis, as precursors to ferromagnetic ceramics [4-6], Moreover, they can by synthesized with a very narrow molar mass distribution, with excellent control over chain length and composition [7], An important feature of PFS is that the polymers bearing two methyl groups on the silane unit are crystalline, whereas polymers with two different substituents on each silane (methyl, ethyl methyl, phenyl) are atactic and remain amorphous. This feature of the polymer composition has a strong influence on the type of self assembled structures that these poly-... 

For polymers, DT is found to be virtually independent of chain length and chain branching, but it is strongly dependent on polymer and solvent composition [84]. For random copolymers, DT varies linearly with monomer composition block copolymers display more complex behavior [111,214]. For segregated block copolymers like micelles, DT seems to be determined by the monomers located in the outer region (see Fig. 18). For particles, DT appears to be both composition and size dependent [215]. 

---