Chain architectures

Polymers without configurational regularity are called atactic. Configurationally regular polymers can fonn crystalline stmctures, while atactic polymers are almost always amorjihous. Many polymers consist of linear molecules, however, nonlinear chain architectures are also important (figure C2.1.2). 

Figure C2.1.2. Polymers witli linear and nonlinear chain architectures. The nonlinear polymers can have branched chains. Short chains of oligomers can be grafted to tire main chain. The chains may fonn a. stor-like stmcture. The chains can be cross-linked and fonn a network.

CR 3nd tp are the contributions from chain recoiling and interfacial dynamics (i.e. drag forces and disentanglement), respectively, and / ve is the viscoelastic loss function which has interfacial and bulk parts. / is a characteristic length of the viscoelastic medium, t is the contact time and n is the chain architecture factor. Fig. 21 illustrates the proposed rate dependency of adhesion energy. 

We present here a simple experiment, conceived to test both the reptation model and the minor chain model, by Welp et al. [50] and Agrawal et al. [51-53]. Consider the HDH/DHD interface formed with two layers of polystyrene with chain architectures shown in Fig. 5. In one of the layers, the central 50% of the chain is deuterated. This constitutes a triblock copolymer of labeled and normal polystyrene, which is, denoted HDH. In the second layer, the labeling has been reversed so that the two end fractions of the chain are deuterated, denoted by DHD. At temperatures above the glass transition temperature of the polystyrene ( 100°C), the polymer chains begin to interdiffuse across the... 

In some of these models (see Sec. Ill) the surfactants are still treated as flexible chains [24]. This allows one to study the role of the chain length and chain conformations. For example, the chain degrees of freedom are responsible for the internal phase transitions in monolayers and bilayers, in particular the hquid/gel transition. The chain length and chain architecture determine the efficiency of an amphiphile and thus influence the phase behavior. Moreover, they affect the shapes and size distributions of micelles. Chain models are usually fairly universal, in the sense that they can be used to study many different phenomena. 

The chain architecture and chemical structure could be modified by SCVCP leading to a facile, one-pot synthesis of surface-grafted branched polymers. The copolymerization gave an intermediate surface topography and film thickness between the polymer protrusions obtained from SCVP of an AB inimer and the polymer brushes obtained by ATRP of a conventional monomer. The difference in the Br content at the surface between hyperbranched, branched, and linear polymers was confirmed by XPS, suggesting the feasibility to control the surface chemical functionality. The principal result of the works is a demonstration of utility of the surface-initiated SCVP via ATRP to prepare surface-grafted hyperbranched and branched polymers with characteristic architecture and topography. 

Owing to multi-functionahty, physical properties such as solubihty and the glass transition temperature and chemical functionahty the hyperbranched (meth) acrylates can be controlled by the chemical modification of the functional groups. The modifications of the chain architecture and chemical structure by SCV(C)P of inimers and functional monomers, which may lead to a facile, one-pot synthesis of novel functionahzed hyperbranched polymers, is another attractive feature of the process. The procedure can be regarded as a convenient approach toward the preparation of the chemically sensitive interfaces. 

The influence of the copolymer chain architecture on the CMC has been investigated in PEO- and PBO-containing bock copolymers, as schematically depicted in Fig. 1. From an entropic point of view, the formation of micelles should be favored for diblock architectures compared to triblock and cyclic ones, the reason being that two block junctions should reside at the... 

Anion-mediated hydrogen-bonded 1-D chain architectures. 

A remarkable facet of the extended structures of these species is the fact that an elegant 2-D sheet architecture featuring rhombic (4,4) networks is common to fourteen of the sixteen compounds (Table 2). The other two complexes, [Cu(Lee)2]Cl2-H20 and [Cu(Lee)2]Br2 MeOH, adopt totally different 1-D chain architectures. 

Man, however, was by far not the first to recognize the tremendous potential of giant chain architectures millions of years ago, nature developed macromol-... 

At the same time, the macromolecules might be classified according to whether their chains have only one kind of atoms - like carbon - in the backbone (isochains) or different elements (heterochains). Concerning their chain architecture, polymers are subdivided into linear, branched, comb-like, crosslinked, dendritic, or star-like systems. 

Highly Spatioresolved Graft-Chain Architectures Analogue Models of Tree Growth Progression... 

Fig. 7 Maltotetraose hybrids with various carriers resulting in different chain architectures A poly(ethylene oxide) Ba and Bb poly(acrylic acid), amylose, cellulose, and other polysaccharides Ca cyclodextrin and multifunctional acids Cb amylopectin D crosslinked poly(acryl amide) [156] - Reproduced by permission of Wiley...

Polymers can be made that contain more than one type of repeat unit. For example, the R group on the asymmetric carbon in Figure 1.56 could be chlorine in some of the monomer units and fluorine in the rest. Such polymers are called copolymers. The ratio of the two types of monomers can vary from 0 to 1, and there can be more than two types of monomers in a copolymer. The presence of more than one type of repeat unit opens up many possibilities for variation in the structure of the polymer, or chain architecture as it is sometimes called. We will not describe the myriad of possible variations and the important consequences in terms of polymer physical properties, but here merely categorize copolymers in some broad, structural terms. 

IV. Characterization of Polymers with Differing Chain Architectures. . . . 208... 

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