Polymers boat form

Several examples are known, in which one or even both monomers in a liquid crystalline [A-B]n condensation polymer contain cyclo-aliphatic rings [50]. The trans chair form makes a larger contribution than the cis boat form. 

Ghosh and Bharadwaj [143] described discrete hexameric water clusters with puckered-boat conformation acting as pillars between 2-D copper(n) coordination polymers to form a stable 3-D metal-organic j amework. 

The polymer had primarily trans configuration and contained the cyclohexane ring in the boat form. On the other side, polymerization of 5-methyl-substituted bicyclo[2.2.2]octene has been carried out with cationic and Ziegler-Natta systems [146] leading to low yields in polymers, probably of mainly vinylic structures. 

Fiber-reinforced composites contain strong fibers embedded in a continuous phase. They form the basis of many of the advanced and space-age products. They are important because they offer strength without weight and good resistance to weathering. Typical fibers are fiberous glass, carbon-based, aromatic nylons, and polyolefins. Typical resins are polyimides, polyesters, epoxys, PF, and many synthetic polymers. Applications include biomedical, boating, aerospace and outer space, sports, automotive, and industry. 

A common example of a plasticized polymer is poly(vinyl chloride). The common atactic form has a Tg of about 80 °C, well above room temperature. Without a plasticizer, vinyl is stiff and brittle. Dibutyl phthalate (see the structure at left) is added to the polymer to lower its glass transition temperature to about 0 °C. This plasticized material is the flexible, somewhat stretchy film we think of as vinyl raincoats, shoes, and even inflatable boats. Dibutyl phthalate is slightly volatile, however, and it gradually evaporates. The soft, plasticized vinyl gradually loses its plasticizer and becomes hard and brittle. 

Although enormous quantities of man-made fibers and elastomers are produced each year, the major consumption of synthetic polymers is as plastics, materials used in the form of sheets, pipes, films, and, most important of all, molded objects toys and bottles knobs, handles, and switches dishes, fountain pens, toothbrushes valves, gears, bearings cases for radios and television sets boats, automobile bodies, and even houses. 

Dichroic Behavior of Carboxyl and Amide Chromophores in Polysaccharide It is evident that the configurational differences of the uronic acid moiety are well reflected in the dichroic behavior of the polymer, and the carboxyl chromophore thus plays a significant role in the chiroptical properties of the molecules. Certain facts regarding carboxyl chromophores are apparent from this study a) monomeric CD properties are well reflected in the Cotton effect of the polymer b) similarities in A0 values (Table 11) between monomers and polymers containing similar uronic acids indicate the additivity of monomer contributions to polymer CD c) iduronic acid shows considerably larger CD than glucuronic acid, which may have some origin in the observed difference in the NMR behavior (29) of methyl a-D-idopyranosiduronic acid from uronic acid with normal C-1 conformation. This has been interpreted in terms of either an equilibrium between the C-1 and 1-C chair forms or adoption of a hybrid skew boat structure. 

One of the ultra-high modulus fibre forming polymers, designated H, contains non-aromatic piperazine rings which in principle could be in either of the two interconvertible conformations known as boat and chair . A further complication is introduced by the possibility of cis and... 

Other tertiary recycling processes that have been developed include a Freeman Chemical Corp. process to convert PET bottles and film to aromatic polyols used for manufacture of urethane and isocyanurates. Glycolized PET, preferably from film, since it is often lower in cost than bottles, can be reacted with unsaturated dibasic acids or anhydrides to form unsaturated polyesters. These can then be used in applications such as glass-fiber-reinforced bath tubs, shower stalls, and boat huUs. United States companies that have been involved include Ashland Chemical, Alpha Corp., Ruco Polymer Corp., and Plexmar. Unsaturated polyesters have also been used in polymer concrete, where the very fast cure times facilitate repair of concrete structures. Basing polymer concrete materials, for repair or precast applications, on recycled PET reportedly leads to 5 to 10 percent cost savings and comparable properties to polymer concrete based on virgin materials. However, they are still approximately 10 times the cost of portland cement concrete. There appears to be little commercial application of these processes at present. 

Fishermen periodically recover chemical weapons and are burned through accidental exposure to sulphur mustard. This is because when sulphur mustard comes in contact with cold water a tarry substance forms around the exterior while the interior remains viscous over a period of many decades. The exterior consists mainly of precipitates derived from thickening agents (Fishermen then break open the crusty exteriors as they haul their catches into their boats and may then become exposed or contaminate their vessels as a result). The chemical composition of the tarry exterior is not well understood partly because it varies from case to case. Various polymer materials, such as alloprene and poly [methyl methacrylate] (PMMA), for example, were sometimes combined with sulphur mustard to lower its freezing temperature. Solvents such as chlorobenzene, have also been combined with sulphur mustard. Finally, sulphur mustard was often mixed with arsenic-containing agents, such as lewisite and diphenychloroarsine. 

Cross-linked pol)uners are formed when long chains are linked in one gigantic, three-dimensional structure with tremendous rigidity. Addition and condensation polymers can exist with a cross-linked network, depending on the monomers used in the synthesis. Familiar examples of cross-linked polymers are Bakelite, rubber, and casting (boat) resin. The process can be represented as follows ... 

The zinc enamine EtZn(Bu NHCH=CHNEtBu ), obtained from Et2Zn and Bu N=CHCH=NBu , forms dimeric zinc-aldolates on reaction with aldehydes. The dimeric zinc-aldolate fromp-HCOCsHtN forms a coordination polymer with Vi equivalent Et2Zn. The X-ray structure of the polymer, in which the pyridine nitrogens are coordinated to bridging Et2Zn units, shows the monomeric zinc-aldolate units to have a distorted boat conformation. The synthesis and characterisation of trimeric [1-EtZnNH-naphthalene.THF]3 (7) and [EtZnP(cyclohexyl)2]j.THF (8), have been described (7) contains 4-coordinate Zn and a cyclic Zn N3 core while in (8), which has a cyclic Zn3 3 ccrystal structure of (2-IZn-l,3-xylene)-1 S-crown-4 has also been reported. ... 

---