Simultaneous Chain-Growth and Step-Growth Polymerization of Methoxystyrenes by Rare-Earth Catalysts

2016 ◽  
Vol 128 (47) ◽  
pp. 15032-15037 ◽  
Author(s):  
Xiaochao Shi ◽  
Masayoshi Nishiura ◽  
Zhaomin Hou
Keyword(s):  
Rare Earth ◽  
Chain Growth ◽  
Step Growth ◽  
Step Growth Polymerization

Step-growth polymerization—basics and development of new materials

2004 ◽  
Author(s):  
Zhiqun He ◽  
Eric A . Whale
Keyword(s):  
Molecular Weight ◽  
Degree Of Polymerization ◽  
Average Degree ◽  
Chain Growth ◽  
Side Reactions ◽  
Growth Processes ◽  
Molecular Weights ◽  
Reactive Groups ◽  
Step Growth ◽  
Step Growth Polymerization

Step-growth polymerization is often referred to as condensation polymerization, since often—but by no means always—small molecules such as water are released during the formation of the polymer chains. There are a number of differences in the way polymerization occurs in step-growth polymerization compared to chain-growth processes, and these have marked practical implications. The most obvious difference is that, as the name implies, the polymer chain grows in a step-wise fashion; the initial stage of the reaction involves the conversion of monomers to dimers and from these other lower molecular weight oligomers. It is only as the reaction nears completion that significant quantities of higher molecular weight material can be formed. Thus, in order to obtain effective molecular weights, the reaction must proceed almost to completion, indeed the molecular weight (in terms of the number average degree of polymerization xn) of the polymer can be linked to the extent of reaction (p) using eqn (1). Thus, in the simplest case of a difunctional (AB) monomer, when 50% of the available groups have reacted, the number average degree of polymerization is only 2. The consequence of eqn (1) is that high molecular weights in step-growth polymerizations are associated with highly efficient reactions that do not have side-reactions. Notwithstanding this, the types of molecular weights associated with chain-growth processes are not encountered in these processes (except in the case of monomers with more than two reactive groups where hyper-branched or even cross-linked polymers are possible). There is an additional complication, namely the role of cyclization. Kricheldorf has recently shown that under perfect conditions cyclization is the ultimate fate of any polymerization reaction. Thus, under extremely high conversions the prediction given by eqn (1) would overestimate the actual molecular weights produced. Molecules that undergo step-growth polymerization must have at least two reactive functional groups. If the functionality is greater than this, for example, trifunctional, then hyperbranched polymers or even cross-linked systems can be formed. Commonly, this involves the reaction of two different reactive difunctional monomers.

Stimuli responsive triblock copolymers by chain-growth polymerization from telechelic macroinitiators prepared via a step-growth polymerization

2014 ◽  
Vol 5 (12) ◽  
pp. 3901-3909 ◽  
Author(s):  
Krishna Dan ◽  
Suhrit Ghosh
Keyword(s):  
Block Copolymers ◽  
Triblock Copolymers ◽  
Chain Growth ◽  
Stimuli Responsive ◽  
Step Growth ◽  
Step Growth Polymerization ◽  
A Chain

The synthesis of stimuli-responsive ABA tri-block copolymers using a step-growth polmerization followed by a chain-growth polymerization.

Polymer Chemistry

2004 ◽  
Keyword(s):  
Conducting Polymers ◽  
Liquid Crystalline ◽  
Polymer Chemistry ◽  
Chain Growth ◽  
Crystalline Polymers ◽  
Wide Range ◽  
Cyclic Oligomers ◽  
Step Growth

Polymer Chemistry: A Practical Approach in Chemistry has been designed for both chemists working in and new to the area of polymer synthesis. It contains detailed instructions for preparation of a wide-range of polymers by a wide variety of different techniques, and describes how this synthetic methodology can be applied to the development of new materials. It includes details of well-established techniques, e.g. chain-growth or step-growth processes together with more up-to-date examples using methods such as atom-transfer radical polymerization. Less well-known procedures are also included, e.g. electrochemical synthesis of conducting polymers and the preparation of liquid crystalline elastomers with highly ordered structures. Other topics covered include general polymerization methodology, controlled/"living" polymerization methods, the formation of cyclic oligomers during step-growth polymerization, the synthesis of conducting polymers based on heterocyclic compounds, dendrimers, the preparation of imprinted polymers and liquid crystalline polymers. The main bulk of the text is preceded by an introductory chapter detailing some of the techniques available to the scientist for the characterization of polymers, both in terms of their chemical composition and in terms of their properties as materials. The book is intended not only for the specialist in polymer chemistry, but also for the organic chemist with little experience who requires a practical introduction to the field.

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