Groups of Polymers

An important group of polymers used as moulding resins and in extruded forms (e.g. film). Can be electroplated. Useful polymerization is by Ziegler catalysis and gives an isotactic material. U.S. production 1983 1 -7 megatonnes. 

Poly(ethylene oxide)—Poly(ethylene terephthalate) Copolymers. The poly(ethylene oxide)-poly(ethylene terephthalate) (PEO/PET) copolymers were first described in 1954 (40). This group of polymers was developed in an attempt to simultaneously reduce the crystallinity of PET, and increase its hydrophilicity to improve dyeabiHty. PEO/PET copolymers with increased PEO contents produce surfaces that approach zero interfacial energy between the implant and the adjacent biological tissue. The coUagenous capsule formed around the implant is thinner as the PEO contents increase. The stmcture of a PEO/PET copolymer is shown below ... 

The simplest linear-chain polymer is polyethylene (Fig. 22.3a). By replacing one H atom of the monomer by a side-group or radical R (sausages on Fig. 22.3b, c, d) we obtain the vinyl group of polymers R = Cl gives polyvinyl chloride R = CIT3 gives... 

Unsaturated polyesters are a group of polymers and resins used in coatings or for castings with styrene. These polymers normally have maleic anhydride moiety or an unsaturated fatty acid to impart the required unsaturation. A typical example is the reaction between maleic anhydride and ethylene glycol ... 

Crosslinking using reactions of multifunctional reagents with side groups of polymers is most frequently applied to PVA, some biopolymers containing OH-groups, partly hydrolyzed PAAm, polyamines, and other polymers. These reactions are reviewed in Ref. [52],... 

Methacrylates and acrylates are a large group of polymers that together form acrylic plastics used in many common household products. 

Phenol, along with formaldehyde, is used to produce a very important and versatile group of polymers known as phenolics or phenol-formaldehyde resins. These resins can be either thermoplastic or thermosetting, depending on the amount of formaldehyde used. A larger ratio of formaldehyde to phenol promotes crosslinking to produce more rigid materials. 

So far only a small number of backbone-modified poly (amino acids) have been prepared and carefully characterized. This chapter therefore represents an account of the initial investigations of this interesting and promising group of polymers. 

The most studied class of boron polymers containing boron-silicon bonds are the carboranylenesiloxane polymers. The history of these polymers was discussed at the beginning of this chapter. The more recent advances in this group of polymers and in silicon-containing borazine and boroxine polymers are discussed in later sections of this chapter. In this section, some remaining groups of silicon-containing boron polymers are discussed. 

Figure 22 H NMR spectrum from di-hydroxyl end-capped PPG. Inset shows expansion of spectrum indicating assignments for allyl end groups of polymer.

Mechanisms Leading to the Light Emission from Thermally Oxidized Polymers (Chemiluminescence), Similarities and Differences within Respective Groups of Polymers 463... 

MECHANISMS LEADING TO THE LIGHT EMISSION FROM THERMALLY OXIDIZED POLYMERS (CHEMILUMINESCENCE), SIMILARITIES AND DIFFERENCES WITHIN RESPECTIVE GROUPS OF POLYMERS... 

In addition to homolytic decomposition, hydroperoxyl groups of polymer are decomposed in reactions with alkyl radicals (see Chapter 4). Such induced decomposition of POOH groups... 

Fig. 45. [t ] and content of pendant vinyl groups of polymers shown as a function of the initial n-BuLi concentration in the anionic polymerization of 1,4-DVB in THF. Initial 1,4-DVB concentration = 20 g/L. Reaction temperature = -78 °C. Reaction time = 7 min. [Reproduced from Ref. 231 with permission, Hiithig Wepf Publ., Zug, Switzerland]. 

The structures of 23a and 23x used in the calculations are octamer or nanomer constructed based on X-ray data for 23a. Enantiomers were generated on the middle part of the polymers in order to avoid the influence of the end groups of polymers, because 23a and 23x used as the CSPs are polymers with degree of polymerization of 200. 

It is possible that polar or polarizable side-groups of polymers, e.g., RO from VE, can complex with the growing cations, but for the reasons explained (Plesch 1993) this effect will not be considered in detail (see also Section 3a). 

The object of the work described was to discriminate between the two principal rival theories concerning the polymerisation of 1,3-dioxacycloalkanes by anhydrous perchloric acid, the Mainz theory and the Keele theory . By means of Jaaks s method for determining tertiary oxonium ions we found that in polymerisations under the driest conditions the concentration of these is negligibly small. This was done with 1,3-dioxolane (1), 4-methyl-l,3-dioxolane (4), and 1,3-dioxepane (5), and the findings are supported by determinations of the content of hydroxy groups of polymers prepared and killed under different conditions. 

Some of the first questions that arise when looking at a new group of polymers such as hyperbranched polymers concern the glass transition temperature -what determines it, what molecular motions determine it, is there a difference in Tg for different parts of the molecule Since hyperbranched polymers are almost exclusively amorphous materials, the glass transition temperature will be one of the most important features. 

Polysaccharides were the first group of polymers considered. Dextrans, polymers of glucose synthesized from sucrose, are Important Industrial polysaccharides ( ) ... 

Many polymers, such as cellulose and HDPE, are linear polymers considering long, continuous, covalently bonded atoms. Others may be branched or cross-linked. Both linear polymers and those with branching are generally thermoplastics that can be remolded by application of heat and pressure. Others that are cross-linked are thermosets that cannot be remolded by application of heat and pressure. Both groups of polymers can be recycled, but it is easier to recycle thermoplastic materials. 

For some important groups of polymers, special names and systems of nomenclature were developed. For instance, the nylons were named according to the number of carbons in the diamine and dicarboxylic acid reactants used in their synthesis. The nylon produced by the condensation of 1,6-hexamethylenediamine (6 carbons) and adipic acid (6 carbons) is called nylon-6,6. Even here, there is no set standard as to how nylon-6,6 is to be written with alternatives including nylon-66 and nylon-6,6. 

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