Polymers with branches

Miktoarm star (or p-star) polymers are star polymers with branches of different polymers. These polymers are also called heteroarm or mixed-arm star polymers. Their synthesis is more difficult but success has been achieved by sequential coupling [Hadjichristidis, et al., 1999]. To obtain a 3-arm star with one polyisoprenyl (PI) and two polystyryl (PS) branches, polyisoprenyllithium is reacted with an excess of CH3SiCl3 to form the one-arm polymer, the unreacted CH3SiCl3 is removed, and then polystyryllithium is added ... 

Branched chains occupy more volume than linear chains, and the viscosity of polymers with branched chains is less than that of those with linear chains. The viscosities of polymer solutions are greater than those of solvents. 

The relative sensitivity of short-chain alkyl branches of different sizes to elimination on irradiation with formation of the corresponding alkane has been variously reported as being constant or varying (13,14). Figure 9 compares G values for formation of the alkane corresponding to the short-chain branch from samples of these three polymers with branch frequencies from 0.5 to 6 per 1,000 C atoms. There is a notably higher scission efficiency for ethyl branches. 

A polymer network can be envisioned as a polymer molecule with an infinite molecular weight [1]. Crosslinking is a physical or chemical route by which polymers with branched or crosslinked structures are produced. The chemical route may imply a polymerization or postpolymerization stage [2-4]. Crosslinking is especially important from the commercial point of view. Polymer networks may... 

Zimm and Stockmayer [1949] also derived theoretical expressions for monodisperse and polydisperse randomly branched polymers with branch functionalities of 3 and 4. 

Bulk mechanochemistry. Unlike linear polymers, the activation of mechanophore in nonlinear macromolecules in bulk is almost blank. Recently, May found that polymers with branched architectures activate more slowly than linear counterparts in solution, yet more quickly in solid-state tensile experiments [198]. In the bulk, more factors take part in the chain degradation event, including but not limited to chain entanglements, phase separation, crystallization, and supramolecular interactions. Inspections in this direction can aid the design of mechanoresponsive materials in the solid state. 

Silicone resins and rubbers ctre cross-linked polymers with branched polymer chains containing M (monofunctional), D (difunctional), T (trifunctional), and Q (tetrafunctional) units. Slightly branched polymers made from D, T, and Q structures have lower bulk viscosity and intrinsic viscosity than linear polymers of the same average molecular weight. 

Branched polymer A polymer with branches having the same repeating units as the main chain. 

The role of chemical effect has also been looked into using fluorocarbon polymers with different structures. The results indicate that the higher peel strengths noted for the polymers with branched... 

MALDI can be used to differentiate polymers with different architectures. For instance, the MALDI spectrum of a polymer made exclusively of linear chains differs from the MALDI spectrum of a polymer with branched chains since linear chains possess two end groups, whereas branched chains possess three, four, five, and so on end groups [51-53]. 

It may be noted that the point for poly(2-ethyl butyl methacrylate) in Fig. 12-5 falls above the line the friction coefficient for this polymer with branched side... 

It is also possible to form star-shaped polymers with several unbranched arms radiating from a single point, or dendritic polymers with branched arms in the star. 

Polymers with branched alkanes as recurrent units, as in polypropylene, react with peroxides by an intra-molecular zip reaction. Fig. 4.44. This intra-molecular shifting of hydrogen atoms encourages the formation of hydrogen peroxides. 

An appropriate overall amphiphilic balance in a polymer chain may be a key to successful sensitive phase separation. This concept was evidenced by phase separation behavior of a polymer with an alcohol pendant having a fine balance between hydrophilidty and hydrophobicity. Ahydroxybutyl group is a rearrangement of an ethoxyethyl unit, and is expected to have a similar overall amphiphilic balance. Aqueous solutions of 23 (Figure 17) underwent rapid phase separation at 42 ° The corresponding polymer with branched alcohol pendants showed a lower critical temperature. Another type of polymers with fine-tuned amphiphilidty would be random copolymers of hydrophobic... 

The so-called in-out method based on DVB provides good access to rather well-defined star-shaped polymers with branches of different chemical nature... 

The term star polymers denotes a polymer with branches emanating from a common source or core. The first star polymers were synthesized by coupling living polymer chain ends with polyfunctional molecules (e.g., polystyryl lithium with SiC ) [21,22]. Multiarm star polymers were synthesized by reacting a living chain end [e.g., poly(butadienyl) lithium] with divinylbenzene. 

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