Macromolecular architectures for

Beside synthetic features, the investigation of unprecedented physical behavior resulting directly from the presence of defined topological bonds is particularly exciting. The most directly accessible macromolecular architecture for physical measurements is the poly[2]catenane 10, because poly[2]catenanes containing... 

On that basis, the book intends to bridge current issues, aspects and interests from fundamental research to technical apphcations. In seven chapters, the reader will find an arrangement of latest results on fundamental aspects of adhesion, on adhesion in biology, on chemistry for adhesive formulation, on surface chemistry and pretreatment of adherends, on mechanical issues, non-destructive testing and durability of adhesive joints, and on advanced technical applications of adhesive joints. Prominent scientists review the current state of knowledge about the role of chemical bonds in adhesion, about new resins and nanocomposites for adhesives, and about the role of macromolecular architecture for the properties of hot melt and pressure sensitive adhesives. Thus, insight into detailed results and broader overviews as well can be gained from the book. 

The Preparation and Investigation of Macromolecular Architectures for Microlithography by Living Free Radical Polymerization... 

Hedrick, J.L., et al., 2002. Application of complex macromolecular architectures for advanced microelectronic materials. Chemistry — A European Journal 8 (15), 3308—3319. 

Barclay, G. G., et al. (1998). The preparation and investigation of macromolecular architectures for microlithography by living free radical polymerization. ACS Symp. Ser., 706(Micro- and Nanopatterning Polymers) 144—160. 

Hedrick, J.L., TroUsas, M., Hawker, C.J. et al. (1998) Dendrimer-like star block and amphiphiUc copolymers by combination of ring opening and atom transfer radical polymerization. Macromolecules, 31,8691-8705. Hedrick, J.L., Magbitang, T., Connor, E.F. et al. (2002) Application of complex macromolecular architectures for advanced microelectronic materials. Chemistry - A European Journal, 8,3308-3319. 

Cyclic polymers represent a special class of macromolecules among the various possible polymeric architectures. Because of the absence of chain ends in cyclic polymers, different chain dynamics can strongly influence physical properties compared with linear analogs of the same mass [95]. Recently, therefore, large cyclic polymers have emerged from the realm of scientific curiosities to that of potentially useful macromolecular architectures for a variety of functional applications [96-99]. By virtue of the lUPAC definition [1], cyclic polymers can be considered as macrocycles. Polymers with (small or large) cyclic repeating units within the macromolecular backbone, cyclopolymers, have been known for some time [100-104], and they must not be assimilated to cyclic polymers. 

The authors deeply appreciated the help of Thomas Steward in the Digital Instruments for supplying the software. Thanks to DOW Chemical Company for providing the samples. Thanks are also due to the funding support from U.S. Army Research Office/U.S. Army Research Laboratory-funded Macromolecular Architecture for Performance MAP) Multidisciplinary University Research Initiative (MURI). 

Similar patterns of property differentiation are clearly recognized at the macromolecular level. For example, dramatic changes in physical and chemical properties are observed by simply converting a linear topology of common composition to a cross-linked architecture. In traditional macromolecular science, these issues were considered apparent and obvious. However, as novel architectures emerged, new architecture-property relationships have not been so clearly articulated and exploited. Prompted by the synthetic accessibility of many new polymeric architectures based on common compositional monomers... 

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 urge of polymer scientists to develop new materials is driven by society s wish to substitute conventional materials by plastics and thereby gain in performance. One reason for the emerging interest in hyperbranched polymers and other macromolecular architectures is their different properties compared to conventional, linear polymers. 

Tbe discussion of the semi-chlute properties remains confined mainly to the osmotic modulus which in good solvents describes the repulsive interaction among the macromolecules as a function of concentration. After scaling the concentration by the overlap concentration c = A2M.Yf) and normalizing the osmotic modulus by the molar mass, universal masteS" curves are obtained. These master curves differ characteristically for the various macromolecular architectures. The branched materials form curves which lie, as expected, in the range between hard spheres and flexible linear chains. 

Protein polymers based on Lys-25 were prepared by recombinant DNA (rDNA) technology and bacterial protein expression. The main advantage of this approach is the ability to directly produce high molecular weight polypeptides of exact amino acid sequence with high fidelity as required for this investigation. In contrast to conventional polymer synthesis, protein biosynthesis proceeds with near-absolute control of macromolecular architecture, i.e., size, composition, sequence, topology, and stereochemistry. Biosynthetic polyfa-amino acids) can be considered as model uniform polymers and may possess unique structures and, hence, materials properties, as a consequence of their sequence specificity [11]. Protein biosynthesis affords an opportunity to completely specify the primary structure of the polypeptide repeat and analyze the effect of sequence and structural uniformity on the properties of the protein network. 

Another procedure for the preparation of modified thermosets consists of introducing preformed particles in the initial formulation. This technique is also well documented for modified thermoplastics (Paul and Bucknall, 2000). In Chapter 7 different macromolecular architectures such block copolymers, crosslinked microparticles, hyperbranched polymers, and den-drimers, were presented (Fig. 7.11). All these compact molecules can be used as thermoset modifiers. Thermoplastic powders and core-shell polymers are the more accessible preformed molecules. Some examples are given below. 

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