Branched architecture

Smith DK, Diederich F (2000) Supramolecular Dendrimer Chemistry - A Journey Through the Branched Architecture. 210 183-227 Stec WJ, see Guga P (2002) 220 169-200 Steudel R (2003) Aqueous Sulfur Sols. 230 153-166 Steudel R (2003) Liquid Sulfur. 230 80-116... 

For example, the parameters g = 0.77, h = 0.94, p = 1.4, and C = 0.158 measured for a polymer sample and compared with the plots in Figures 7.11 through 7.13 were most consistent with athree-arm star monodisperse polymer a poly disperse three-arm star would have g= 1.12,/ = 1.05,p= 1.6, and C close to 0.2. °° The second example was poly(vinyl acetate) (PVAc) prepared by emulsion polymerization. Since no data for linear equivalent were available, g and h were not calculated. At lower conversion/MW p= 1.84 was found, only slightly higher than the theoretically expected p = 1.73 for a randomly branched architecture, p slightly decreased with increasing M, indicating... 

LCB polymers can be formed by chemically linking preformed polymers (arm first or polymer first method) or by growing polymer chains from a multifunctional initiatior (core first method). In both cases living polymerization techniques are preferred because they provide better control over MW, MW distribution and the final branching architecture. However, highly selective coupling reactions e.g. with multifunctional isocyanates, or dicyclohexylcar-bodiimide (DCC) coupling, have also been successful. 

To increase the elongational viscosity of PET and PBT resins by facilitating extended and branched architectures... 

Dendritic polymers are most often reported to be amorphous, which can be anticipated from their highly branched architecture. However, some exceptions are presented in the literature. Percec et al. [34,35] reported on liquid crystalline (LC) hyperbranched polymers where the LC-phase was achieved by conformational isomerism. Various repeat units of A2B type have been used where a flex-... 

If combs represent one extreme of the topological family of branched polymers, then another extreme is given by the case of dendritic polymers, which retain a branched structure at all timescales. The study of tree-like branched architectures is also motivated by the important commercial low density polyethylene (LDPE), which has remarkable rheological properties making it suitable for many processing operations [3]. 

Fig. 17. Damping functions in shear from the tube model for linear polymers (lowest curve) and various branched architectures. In the cases of comb and tree, the lower curves give the case of the structure with four levels of branching, the upper the limit of large structures hatched area covers published results on LDPE...

The final chapter develops the most modern insights in the relation between the rheological properties and the large scale architecture of polymers. Indeed, the largest effects of branching are encountered in their melt relaxation properties. In the absence of reptation, which dominates relaxation processes in Hnear polymers, a rich variety of other relaxation processes becomes apparent. The control ot the melt properties of polymers by means of their long-chain branch architecture will continue to lead to new industrial applications. 

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