Organic polymer structure control

Since almost all conjugated polymers are organic semiconductors, structural control, such as compositional control of a copolymer thin film, corresponds... 

The control of the pore size of porous silica gel by the structure of the organic polymer has been accomplished by using the so-called starburst dendrimer as an... 

A surface is that part of an object which is in direct contact with its environment and hence, is most affected by it. The surface properties of solid organic polymers have a strong impact on many, if not most, of their apphcations. The properties and structure of these surfaces are, therefore, of utmost importance. The chemical stmcture and thermodynamic state of polymer surfaces are important factors that determine many of their practical characteristics. Examples of properties affected by polymer surface stmcture include adhesion, wettability, friction, coatability, permeability, dyeabil-ity, gloss, corrosion, surface electrostatic charging, cellular recognition, and biocompatibility. Interfacial characteristics of polymer systems control the domain size and the stability of polymer-polymer dispersions, adhesive strength of laminates and composites, cohesive strength of polymer blends, mechanical properties of adhesive joints, etc. 

Polymers used in medicine fall into two main categories those that are sufficiently inert to fulfill a long-term structural function as biomaterials or membranes, and those that are sufficiently hydrolytically unstable to function as bioeradible materials, either in the form of sutures or as absorbable matrices for the controlled release of drugs. For the synthetic organic polymers widely used in biomedicine this often translates to a distinction between polymers that have a completely hydrocarbon backbone and those that have sites in the backbone that are hydrolytically sensitive. Ester, anhydride, amide, or urethane linkages in the backbone usually serve this function. 

The solid-state polymerization of diacetylenes is an example of a lattice-controlled solid-state reaction. Polydiacetylenes are synthesized via a 1,4-addition reaction of monomer crystals of the form R-C=C-CeC-R. The polymer backbone has a planar, fully conjugated structure. The electronic structure is essentially one dimensional with a lowest-energy optical transition of typically 16 000 cm-l. The polydiacetylenes are unique among organic polymers in that they may be obtained as large-dimension single crystals. 

It is appropriate to compare the well-known concepts of covalent bond formation in traditional organic chemistry with those that apply to classical polymer chemistry and to dendritic macromolecular chemistry. This allows one to fully appreciate the differences between the three areas in the context of structure control, in concert with issues related to terminal group and mass amplification. 

Polymer hypothesis Stereoregulation of polymer structure Organization of polymer chains Synthesis on a solid matrix Polymer structure and control at interfaces Conductive polymers... 

This article deals with the polymer-metal complexes (Schemes 1 —5), because they have the following merits in comparison with other polymeric metal complexes, (i) Metal ion and ligand site can be chosen for study without restrictions, (ii) It is not difficult to control the molecular weight of a polymer complex and to modify the structure of a polymer ligand, (iii) The polymer complex is soluble in both aqueous and nonaqueous solvent, (iv) It is possible to change the ratio of the organic polymer part to the inorganic metal complex part. This explains why the polymer often affects the behavior of the metal complex. 

Carbon molecular sieves are produced by controlled pyrolysis and subsequent oxidation of coal, anthracite, or organic polymer materials. They differ from zeolites in that the micropores are not determined by the crystal structure and there is therefore always some distribution of micropore size. However, by careful control of the manufacturing process the micropore size distribution can be kept surprisingly narrow, so that efficient size-selective adsorption separations are possible with such adsorbents. Carbon molecular sieves also have a well-defined bi-modal (macropore-micropore) size distribution, so there are many similarities between the adsorption kinetic behavior of zeolitic and carbon molecular sieve systems. 

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