Heterogeneous branching

Poly(ADP-ribose) (PAR) is a heterogenous branched polymer of repeating ADPR units linked via glycosidic ribose-ribose 1" 2 bonds in the linear chain and... 

Fig. 61. a Model of a heterogeneously branched macromolecuie and b a detail of the strucutre95 ... 

The details of these latter thermally activated, surface-catalyzed, heterogeneous branching chain reactions are complex. Premature reactions in the gas stream before gases reach the heated wafers must be avoided. The reduction of B2O3 by Si at the glass interface releases free B from the glass for doping. 

The effect of branch distribution of LLDPE on the crystallization of HDPE/ LLDPE blends has also been investigated. The DSC and scanning electron microscopy (SEM) studies of Lee et al. (68) found that aZiegler-Natta-catalyzed LLDPE-B having a relatively heterogeneous branch distribution (179,000 Mw, 4.2 PDl, and 16 ethyl branches per 1000 backbone carbons) cocrystallizes with HDPE (147,000 Mw and 3.7 PDl) in a wide range of blend compositions, and at the same time. 

Koizumi, K, T Tanimoto, K Fujita, K Hara, N Kuwahara and S Kitahata (1993). Preparation, isolation, and characterization of novel heterogeneous branched cyclomalto-oligosaccharides having 8-d-galactosyl residue(s) on the side chain. Carbohydrate Research, 238(0), 75-91. 

Heterogeneous branched core-shell Sn02-PAN1 nanorod arrays with mechanical integrity and three dimensional electron transport for Uthium batteries. Nano Energy 8,196-204. 

This document describes a process with one CSTR and one TR, but a single STR may also be used - in the former case a catalyst should be injected to each reactor. While the main catalyst is Z-N type, use of a single-site one may offer additional advantages blending homogeneously and heterogeneously branched chains... 

These data explain the relatively heterogeneous branching distribution of ethylene/1-olefin copolymers prepared with Ti/Mg Ziegler catalysts. For example, the catalyst prepared without silica contained at least five active sites that exhibited a range of r values from 19 to -180, which varies by a... 

Elston used copolymer melting point values to determine the branching homogeneity of copolymers noting that ethylene/1-olefin copolymers with a heterogeneous branching distribution show crystalline melting... 

High activity Ti/Mg catalyst (multi-site) and heterogeneous branching distribution... 

Figure 4.12 Density and 1-hexene content of ethylene/1-hexene copolymers with a heterogeneous branching distribution (—) and homogeneous (solid line) branching distribution [41].

Figure 7.6 DSC melting point scan for LLDPE (containing ca. 3.5 mol% 1-hexene) prepared with high-activity Ti/Mg catalyst. Note The higher melting point crystallites contain relatively less 1-hexene due to heterogeneous branching distribution [12].

Figure 7.8 compares the DSC melting endotherms for each type of branching. The homogeneous sample contained 2.5 mol% 1-hexene, while the heterogeneous branching sample contained 2.8 mol% 1-hexene [13,14]. 

Wild and coworkers reported [19] the wide distribution of branching in two LLDPE resins of commercial importance at the time. Both samples had a density of 0.919 g/cc and similar MI values of 1.0 and 1.2 but were produced with two different low-pressure processes. As expected, polyethylene molecular fractions were found with a very heterogeneous branching distribution from about nil to 44 methyl groups/1000 carbons. The slight differences in the TREE data of the two similar LLDPE samples were attributed to the different process used to produce the sample. 

Hemicellulose (30kDa) is the glue in the cellulose fibers it has shorter, branched polymer chains built up from a variety of hexoses and pentoses. Tnnlin (lOkDa) is a heterogeneous branched polymer consisting of 3-100 monomers, mainly fructose, Unked via p-2.1-glycosidic bonds. Ahke starch, hemicellulose and inulin are easy to digest via hydrolysis, in contrast to the more resistant nature of cellulose. 

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