Architectural polymer classes

Architectural Polymer Class Polymer Type Repeat Units Covalent Connectivity ... 

It should be quite apparent that, although all major architectural polymer classes are derived from common or related repeat units, the covalent connectivity is truly discrete and different. Furthermore, mathematical analysis of the respective propagation strategies clearly illustrates the dramatic differences in structure development as a function of covalent bond formation. It should be noted that linear, branched, and dendritic topologies differ substantially both in their covalent connectivity, as well as their terminal group to initiator site ratios. In spite of these differences, these open, unlooped macromolecular assemblies clearly manifest thermoplastic polymer type behavior in contrast to the looped, bridged connectivity associated with cross-linked, thermoset systems. In fact, it is now apparent that these three open assembly-topologies (i.e., (I) linear, (III) branched. 

Architectural polymer class Polymer type Repeat units Covalent connectivjty ... 

FIGURE 42.6. Examples of architectural polymer classes (l-IV) polymer type, repeat units, and covalent connectivity associated with architectural classes. (Reproduced from [88] with permission of J. Wiley Sons.)... 

More recently, nontraditional polymerization strategies have evolved to produce a fourth new major polymer architectural class, now referred to as dendritic polymers. This new architectural polymer class consists of four major subsets, namely (a) random hyperbranched, (b) dendrigrafts, (c) dendrons, and (d) dendrimers. Dendrimers, the most extensively studied subset, were discovered by the Tomalia group while at The Dow Chemical Company laboratories (1979). They represent the first example of synthetic, macro-molecular dendritic architecture [33,34]. First use of the term dendrimer appeared in preprints for the 1st SPSJ International Polymer Conference held in Kyoto, Japan (1984). The following year, a full article Polymer Journal, Vol. 17, No. 1, pp. 117-132 (1985)) (see article abstract. Fig. 42.7) described the first preparation of a complete family of... 

Scheme Architecture Polymer class Characteristic Properties Examples...

Covalent polymer networks or (Class II) crosslinked macromolecular architecture polymers rank among the largest molecules known. Their molecular weight is given by the macroscopic size of the object for instance, a car tire made of vulcanized rubber or a crosslinked layer of protective coating can be considered one crosslinked molecule. Such networks are usually called macronetworks. On the other hand, micronetworks have dimensions of several nanometers to several micrometers (e.g. siloxane cages or microgels). 

The folds provide the cell with 1000 self-assembling, complex, diverse atomic architectures that are all compacted into a single polymer class. Each exhibits an exquisite balance of robustness and marginal stability, which makes them eminently adaptable and evolvable and allows allosteric control and a suite of intricate properties ideally suited to the vast range of structural and functional biological roles they... 

Copolymerizations are processes that lead to the formation of polymer chains containing two or more discrete types of monomer unit. Several classes of copolymer that differ in sequence distribution and/or architecture will be... 

An important challenge in the design of novel conjugated polymers is the synthesis of materials with tailor-made solid-state electronic properties. This section outlines the synthesis of the most significant classes of poly(para-phenylenevinylene)s (PPVs), poly(para-phenylene)s (PPPs), and related structures. Furthermore, this review demonstrates that the chromophoric and electronic properties of conjugated rr-systems are sensitive to their molecular and supra-molecular architecture. 

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