Molecular weights of segmented

For a polymer in dilute solution we have seen that 0-5 is proportional to M°Ja, where a is the chain expansion factor (see Chapter 11 note that previously we related °-S to the number of segments, but this is obviously equal to the molecular weight of the chain, M, divided by the molecular weight of segment M. ... 

Several studies have been published in recent years on the properties of RIM polyurethanes and polyurethane-ureas (1-7). Unlike most studies, however, we have restricted our attention to simplified linear systems in order to establish the effect of reaction rates and mold temperatures on the phase separation and molecular weight of segmented polyurethane elastomers produced by RIM(6). 

Degree of cross-linking di- gre 9v kros- link-eg n. The fraction of mer units of a polymer that are cross-linked, equal to the quotient of the mer weight and the average molecular weight of segments between cross-links. 

Slonecki J (1992) The effect of mass fraction and molecular weight of segments on the conditions of preparation, structure and properties of thermoplastic copolyester-ethers (KPEE). Part 111. The effect of mass fraction and molecular weight of segments on some mechanical properties of KPEE, Polimery 37 19-24 (in Polish). 

To the extent that the segmental friction factor f is independent of M, then Eq. (2.56) predicts a first-power dependence of viscosity on the molecular weight of the polymer in agreement with experiment. A more detailed analysis of f shows that segmental motion is easier in the neighborhood of a chain end because the wagging chain end tends to open up the structure of the melt and... 

Lubrication oil additives represent another important market segment for maleic anhydride derivatives. The molecular stmctures of importance are adducts of polyalkenyl succinic anhydrides (see Lubrication and lubricants). These materials act as dispersants and corrosion inhibitors (see Dispersants Corrosion and corrosion control). One particularly important polyalkenyl succinic anhydride molecule in this market is polyisobutylene succinic anhydride (PIBSA) where the polyisobutylene group has a molecular weight of 900 to 1500. Other polyalkenes are also used. Polyalkenyl succinic anhydride is further derivatized with various amines to produce both dispersants and corrosion inhibitors. Another type of dispersant is a polyester produced from a polyalkenyl succinic anhydride and pentaerythritol [115-77-5]. 

Increasing the molecular weight of polyester (or polyether) or changing its chemical composition could lower the Tg of the TPU and decrease the crystallinity of the polymer. For example, a TPU composed of poly(S-lactone), MDI, and 1,4-butanediol was found to have the lowest degree of crystallinity and, therefore, the best compatibility with PVC when the hard segment in it is 36% by weight [10]. 

Radical polymerizations of macromonomers are greatly influenced by the diffusion control effect [44]. Segmental diffusivity and translational diffusivity of the growing chains of macromonomers are strongly affected by the feed concentration and the molecular weight of the macromonomers. Furthermore, there is little difference in the degree of polymerization between macro-... 

Utilization of another function of the macroinitiator was tried in emulsion polymerization [30]. An MAI composed of PEG (molecular weight of a segment is 1000) linked with AGP units was confirmed to be usable as a surface active initiator (Inisurf) for preparing PSt-b-PEG [30]. A higher molecular weight block copolymer was obtained in comparison with the case of solution copolymerization. 

Polybutadiene-polydimethylsiloxane segmented copolymers were prepared by the reaction of epoxy-terminated PDMS and carboxy-terminated polybutadienes, in refluxing toluene under catalytic action of potassium hydroxide 243). Molecular weights of the copolymers obtained were usually in the low range. No other characterization data were available. 

Preparation and thermal crosslinking reactions of oc, -vinylbenzyl terminated polysulfone-b-polydimethylsiloxane, ABA type block copolymers have been discussed 282,313) However, relatively little characterization was reported. Molecular weights of polysulfone and PDMS segments in the copolymers were varied between 800-8,000 and 500-11,000 g/mole, respectively. After thermal curing, the networks obtained showed two phase morphologies as indicated by the detection of two glass transition temperatures (—123 °C and +200 °C) corresponding to PDMS and polysulfone phases, respectively. No mechanical characterization data were provided. 

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