Polymer architectures control

Winningham MJ, Sogah DY. A modular approach to polymer architecture control via catenation of prefabricated biomolecular segments polymers containing parallel /8-sheets templated by a phenoxathiin-based reverse turn mimic. Macromolecules 1997 30 862-876. 

To synthesise polymers with unusual properties from existing basic monomers one needs to place the monomer units in ordered arrays rather than at random. Thus polymer architecture control remains an important area of research. Possible structural elements include block, graft and comb copolymers as well as star and dendritic/hyperbranched topographies. Potential for such structures in the surface coatings and adjacent industries include use as... 

Using MgCl2-based catalysts for PP developed by Montedison it is possible to achieve control of the 3D structure of the catalyst particle and, as a result, of the obtained polymers. Such a polymer architecture control allows synthesis of new materials with improved properties like heteroplastic olefin copolymers, polyolefin alloys (Catalloy), and polyolefin alloys with non-olefinic polymers, which Montell has called Hivalloy. 

The main benefit of the Dow process was control of the polymer architecture. The polymer from the self-condensation process possessed a linear stmcture, but there were other difficulties. The monomer was cosdy and removal of the cuprous bromide by-product was difficult (17) ultimately, scale-up difficulties terrninated the Dow PPS development. However, there was a growing recognition that PPS was an attractive polymer with an excellent combination of properties. 

More recent examples include end-functionalized multiarmed poly(vinyl ether) (44), MVE/styrene block copolymers (45), and star-shaped polymers (46—48). With this remarkable control over polymer architecture, the growth of future commercial appHcations seems entirely likely. 

Sherwin-Williams has developed such a polymer process control system. The methodology used to accommodate the contrasting requirements has two key elements. First, the software is based on a simple architecture that places the definition of changing reactor hardware elements and characteristics in easily modified configuration files (5). Second, the language uses a small number of basic commands to describe formulations and reactor control. Complex operations are described by reference to commands tables (macros) built using several basic commands or other macros. 

C. J. Hawker and J. M. J. Frechet, Preparation of polymers with controlled molecular architecture. A new convergent approach to dendritic macromolecules, J. Am. Chem. Soc., 112 (1990) 7638-7647. 

R.D. McCullough, R.D. Lowe, M. Jayaraman, and D.L. Anderson, Design, synthesis, and control of conducting polymer architectures structurally homogeneous poly(3-alkylthiophenes), J. Org. Chem., 58 904-912, 1993. 

Since that time, synthetic chemists have explored numerous routes to these statistically hyperbranched macromolecular structures. They are recognized to constitute the least controlled subset of structures in the major class of dendritic polymer architecture. In theory, all polymer-forming reactions can be utilized for the synthesis of hyperbranched polymers however, in practice some reactions are more suitable than others. 

Dendritic polymers, the fourth major architectural class of macromolecules, can be divided into three subclasses. These subclasses may be visualized according to the degree of structural perfection attained, namely (1) hyperbranched polymers (statistical structures, Chapter 7), (2) dendrigraft polymers (semi-controlled structures, reviewed in this chapter) and (3) dendrimers (controlled structures, Chapter 1). 

Variations in the graft polymer architectures are possible by controlling the... 

Amphiphilic polymers studied thus far for this purpose can be broadly classified into amphiphilic block copol5mers and amphiphilic homopolymers. We will discuss both of these types of linear polymer architectures. Another interesting class of polymeric amphiphiles is based on branched architectures, known as dendrimers. The most interesting aspect of dendrimers is that their molecular weight and polydisper-sity can be precisely controlled hence, these systems have the potential to be moved... 

Among the two ionic polymerization techniques mentioned above, a living anionic polymerization should show the best possible control of polymer architecture and composition. Mono dispersed homopolymers, complex-block, graft, star, and miktoarm architectures have been accessible primarily by anionic polymerization methods [22]. They have been used to grow polymer brushes from various small particles such as silica gels graphite,carbon black, and flat surfaces [23-26]. Recent results have been reported on living anionic polymerizations on clay [27] and silica nanoparticles [28,29]. 

Twaites BR, CdlH A, Cunliffe D et al (2004) Thermo and pH responsive polymers as gene delivery vectors effect of polymer architecture on DNA complexation in vitro. J Control Release 97 551-566... 

Hertler WR (1997) Group transfer polymerization for controlled polymer architecture. 

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