Comonomer molecular weight dependence

Section 7 introduces a recently developed on-line coupled gel permeation chromatography (GPC) and NMR system, in which a 500-MHz H NMR spectroscopy is used as a detector for GPC. The system facilitates evaluation of molecular weight dependence of polymer characteristics such as tacticity and comonomer composition and determination of molecular weight without using standard polymer samples. 

The molecular weight dependent of comonomer content in LLDPE has been evaluated to some degree in a number of studies. Wild, Ryle and Knobeloch [25]... 

Hosoda [19] also compared the detailed branching distribution of a LLDPE with that obtained for a LDPE resin. In addition to the 3-D representation, Hosoda expressed the distribution data in the alternate form, that of a contour map. The contour maps for the two resin types are shown in Fig. 43. Once again one observes the extremely broad distribution of comonomer in the LLDPE. This particular sample appears to be tri-modal in character with surprisingly little molecular weight dependence on branching. The LDPE on the other hand is very broad in MWD but extremely narrow in SCB distribution. Here also, no attempt was made to relate the structure to any resin properties, although in another... 

Cycloahphatic diamines react with dicarboxyUc acids or their chlorides, dianhydrides, diisocyanates and di- (or poly-)epoxides as comonomers to form high molecular weight polyamides, polyimides, polyureas, and epoxies. Polymer property dependence on diamine stmcture is greater in the linear amorphous thermoplastic polyamides and elastomeric polyureas than in the highly crosslinked thermo set epoxies (2—4). 

Propenylphenoxy compounds have attracted much research. BMI—propenylphenoxy copolymer properties can be tailored through modification of the backbone chemistry of the propenylphenoxy comonomer. Epoxy resins may react with propenylphenol (47,48) to provide functionalized epoxies that may be low or high molecular weight, Hquid or soHd, depending on the epoxy resin employed. Bis[3-(2-propenylphenoxy)phthalimides] have been synthesized from bis(3-rutrophthalimides) and o-propenylphenol sodium involving a nucleophilic nitro displacement reaction (49). They copolymerize with bismaleimide via Diels-Alder and provide temperature-resistant networks. 

The reactivity of macromonomers in copolymerizalion is strongly dependent on the particular comonomer-macromonomer pair. Solvent effects and the viscosity of the polymerization medium can also be important. Propagation may become diffusion controlled such that the propagation rate constant and reactivity ratios depend on the molecular weight of the macromonomer and the viscosity or, more accurately, the free volume of the medium. 

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. 

Depending on the application, different demands are placed on the melt viscosity of the polymer. For injection molding applications, lower melt viscosities are required than for extrusion applications. For a given comonomer composition and processing temperature, the melt viscosity of the cycloolefin copolymers increases with the mean molecular weight. 

Description A variety of polymers are produced on these large reactors for various applications. The melt index, polymer density and molecular weight distribution are controlled with temperature profile, pressure, initiator and comonomer concentration. Autoclave reactors can give narrow or broad molecular weight distribution depending on the selected reactor conditions, whereas tubular reac-... 

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