Vs. branching

Resins vs. Plastics Thermoplastics vs. Thermoset Homopolymers vs. Copolymers Bifuncrional vs. Polyfunctional Linear vs. Branched vs. Cross-Linked Addition vs. Condensation... 

Table II. Branched Epoxy Resins GPC and Melt Viscosity vs. Branch Concentration...

Figure 4. Weight-average molecular weight vs. branch concentration.

Geometric constraints and related factors including active site accessibility, steiic effects of transition states and diffusion limitation of reactants and products play a crucial role in liquid phase catalyzed reactions [240]. Several examples are presented hereafter for illustration (i) TS-1 is more active in the oxidation of linear vs. branched alcohols [241], and in the epoxidation of linear vs. cyclic olefins [153] (ii) in the presence of TBHP, TS-1 has no activity [242], while Ti-6 is less active than Ti-MCM-41 [243] (iii) large TS-1 particles are less effective catalysts than smaller ones [244]. 

The work also revealed that unlike in conventional systems, there was no substrate inhibition and no critical catalyst concentration loading, which is often brought about by the formation of an inactive catalytic dimer species. The novel catalyst or the presence of CO2 was suggested to be the cause of this effect. Carbon monoxide was found to have a strong effect on the selectivity of linear vs. branched product in the supercritical environment. 

Fig. 6 Strain at break vs. branching agent content of PVC films containing 40 wt. % of linear PBA or branched TMP-based plasticizers. L Linear polyester plasticizer, B Branched polyester plasticizer. Reprinted from [40] with permission of WUey-VCH Verlag GmbH Co. Wiley-VCH Verlag GmbH Co. (2006)...

The use of CO + HjO as an in situ source of H2 via the shift reaction or as a source of reducing electrons with concomitant oxidation of CO to CO2 has recently been explored with homogeneous catalyst solutions. Equations (a) and (b) are modifications (Reppe) of hydroformylation (see 14.6.3) and olefin hydrogenation, respectively. The most effective catalysts for equation (a) are Ru3(CO),2, Rh fCOlig, Ir4(CO)i2 in alkaline THE or MeOH. The first of these shows great selectivity in the formation of linear vs. branched aldehyde . With Rhg(CO),5, the aldehyde is reduced further to the alcohol. A different catalyst based on Co2(CO)g/diphos in polar ether solvents has also been used to catalyze equation (a) with propylene as substrate. ... 

Intramolecular cyclization vs. branching during crosslinking copolymerization... 

The rather few polymer MS/MS studies reported so far have emphasized the information provided on the individual end groups of linear polymers. The fragmentation patterns and repeat imits of the various fragment series may also enable the characterization of block vs. random copolymers, of linear vs. branched structiues, and of unsaturated vs. cyclic oligomers. 

A comparison of linear vs branched chains show the following ... 

Linear branched ratio calculated with linear products cw-2PN, trans-2VN, c -3PN, rrani-3PN, and 4PN vs branched products Z-2M2BN and E-2M2BN 2% 4-PN also observed... 

In a related way, the first intermolecular NHC-catalysed hydroacylation of unstrained alkenes (i.e., styrenes) has been reported. Using the triazolium salt (127) bearing an original 2,6-dimethoxyphenyl moiety, hydroacylation products have been obtained in good to excellent yields and with good to excellent levels of regioselectivity, the ratio (128) (129) (linear vs branched isomers) depending on the electronic nature of the styrene partner. 

Melt rheology offers a spectrum of information about the polymer (or blend), its thermal stability, shear sensitivity, the mechanism of degradation (e.g., chain scission vs. branching and crosslinking), processability, etc. The preferred method of testing is dynamic between cone-and-plate or parallel plates. ... 

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