Vinyl polymers typical examples

A review covers the preparation and properties of both MABS and MBS polymers (75). Literature is available on the grafting of methacrylates onto a wide variety of other substrates (76,77). Typical examples include the grafting of methyl methacrylate onto mbbers by a variety of methods chemical (78,79), photochemical (80), radiation (80,81), and mastication (82). Methyl methacrylate has been grafted onto such substrates as cellulose (83), poly(vinyl alcohol) (84), polyester fibers (85), polyethylene (86), poly(styrene) (87), poly(vinyl chloride) (88), and other alkyl methacrylates (89). 

Disregarding the actual chemical mechanism of each monomer reaction, a good example of polymers made by chain reactions are the vinyl polymers (by definition, polymer made from monomers having the vinyl group CH2=CH-, as the reactive group). Formulae of some typical vinyl polymers were reported in Table 1. 

Plasticixers arc low-molecular-weight liquids that lower the glass transition temperature of a polymer. A typical example is the use of dioctyl phthalate in poly(vinyl chloride) to convert the polymer from a rigid material to a soft, flexible one. It the glass transition of the two components A and B are known, an estimate can be made of the Tg value of the mixture by one or the other of the equations... 

Many kinds of nonbiodegradable vinyl-type hydrophilic polymers were also used in combination with aliphatic polyesters to prepare amphiphilic block copolymers. Two typical examples of the vinyl-polymers used are poly(/V-isopropylacrylamide) (PNIPAAm) [149-152] and poly(2-methacryloyloxyethyl phosphorylcholine) (PMPC) [153]. PNIPAAm is well known as a temperature-responsive polymer and has been used in biomedicine to provide smart materials. Temperature-responsive nanoparticles or polymer micelles could be prepared using PNIPAAm-6-PLA block copolymers [149-152]. PMPC is also a well-known biocompatible polymer that suppresses protein adsorption and platelet adhesion, and has been used as the hydrophilic outer shell of polymer micelles consisting of a block copolymer of PMPC -co-PLA [153]. Many other vinyl-type polymers used for PLA-based amphiphilic block copolymers were also introduced in a recent review [16]. 

Thus for undiluted polymers the relaxation behaviour can be examined over a wider range of apparent frequencies. Similar functions can be constructed for other regions of the phase diagram and other rheological experiments. The method of reduced variables has not been widely tested for aqueous crosslinked polymers. Typically these are polyelectrolytes crosslinked by ionic species. Some of these give rise to very simple relaxation behaviour. For example 98% hydrolysed poly(vinyl acetate) can be crosslinked by sodium tetraborate. The crosslink that forms is shown in Figure 5.31. 

Radical chain polymerizations are characterized by the presence of an autoacceleration in the polymerization rate as the reaction proceeds [North, 1974], One would normally expect a reaction rate to fall with time (i.e., the extent of conversion), since the monomer and initiator concentrations decrease with time. However, the exact opposite behavior is observed in many polymerizations—the reaction rate increases with conversion. A typical example is shown in Fig. 3-15 for the polymerization of methyl methacrylate in benzene solution [Schulz and Haborth, 1948]. The plot for the 10% methyl methacrylate solution shows the behavior that would generally be expected. The plot for neat (pure) monomer shows a dramatic autoacceleration in the polymerization rate. Such behavior is referred to as the gel effect. (The term gel as used here is different from its usage in Sec. 2-10 it does not refer to the formation of a crosslinked polymer.) The terms Trommsdorff effect and Norrish-Smith effect are also used in recognition of the early workers in the field. Similar behavior has been observed for a variety of monomers, including styrene, vinyl acetate, and methyl methacrylate [Balke and Hamielec, 1973 Cardenas and O Driscoll, 1976, 1977 Small, 1975 Turner, 1977 Yamamoto and Sugimoto, 1979]. It turns out that the gel effect is the normal ... 

Vinyl Polymers. Vibromilling of a vinyl polymer in the presence of a polymerizable monomer can yield both graft and block copolymers. A typical example is the graft synthesis caused by vibromilling poly(methyl methacrylate) in the presence of gaseous vinyl chloride at 25° C for 12 h (19-21,38). 

In addition to traditional radical initiated addition polymerizations, cation and/or anion catalyzed addition polymerizations are of great commercial importance, since PE, PP and PS are most frequently produced using this type of polymerization technique (Table 5). In addition to the vinyl monomers, vinyli-dene monomers, in which neither R nor R is hydrogen, can form commercially important polymers. PMMA is a typical example of this type of thermoplastics. 

Template Polymers. Template effects in chelating polymers constitute an interesting development in the field of metal containing polymers. The Template effects are interpreted by the fact that the small molecule is templating a pattern in the macromolecule which can be recognized by the same molecule in a subsequent process. The idea is to prepare a polymer from the metal-chelated monomer, to remove the metal ion, and then to measure the selectivity of the prepared polymer for the metal ion of the template [36]. Typical examples of template systems are 4-vinyl-4 -methylbipyridine (Neckers [36]) and 1-vinyl-imidazole (Tsuchida [37]). These are polymerized in presence of divinylbenzene [36] and appropriate metal salts (Co2+, Cu2+, Ni2+, Zn2+). The template metal ions are removed by acid leaching and the polymer subsequently used for metal ion absorption studies (Fig. 16). 

Fig. 4. Pulsed NMR data for poly(vinyl acetate), as a typical example for polymer relaxation. The glass transition corresponds to the abrupt change in T2 and the high temperature minima in T, and T( curves. Lower temperature minima in T, and Tj curves are attributed to a side group relaxation (reprinted from Ref.11 with permission)...

In peroxyl-free-radical chemistry, H02702 " elimination reactions play a major role (Chap. 8.4). In polymer free-radical chemistry, these reactions are of special interest, because they lead to a conversion of slowly diffusing polymer-derived radicals into the readily diffusing HCV/CV radicals. The H02 /02 "-elimina-tion typically proceeds from an a-hydroxyalkylperoxyl radical [reaction (22)]. In poly(vinyl alcohol), for example, such an structural element is formed by H-abstraction and subsequent 02 addition [reactions (18) and (19)]. The same structural element may also be formed during the bimolecular decay of peroxyl radicals which carry an H-atom in [3-position [reactions (20) and (21)]. 

Typical examples of thermosetting polymers are phenolic and urea-formaldehyde resins, unsaturated polyesters, and epoxy resins. Typical thermoplastics are polyethylene, polypropylene, polystyrene, and poly(vinyl chloride). The thermoplastic or thermosetting character of a polymer... 

The reaction of high polymers is another research field of molecular engineering of polymers. In classical polymer chemistry, the synthesis of poly(vinyl alcohol) by hydrolysis of poly(vinyl acetate) may be quoted as a typical example. The chemistry of polymer reactions is still advancing, and many interesting studies are being carried out. In this chapter, a study of Smith et al.55) is described, which illustrates the characteristics of polymer reactions and the production of a functional polymer. 

A typical example showing that we are able to build macromolecules at will is given by C. P. Pinazzi and co-workers in the first chapter of the second section, Chapter 27. They report how model polyenes can be built and how they react. In Chapter 28 K. F. O Driscoll illustrates the limitations in polymerization. For every vinyl monomer, a ceiling temperature exists, above which depropagation exceeds polymerization. If two vinyl monomers are copolymerized at a temperature at which one depropa-gates, the polymer formed will have an unusual composition and sequence distribution. 

Several examples have recently been reported of vinyl-substituted crowns that were polymerized under anionic conditions to pendant crown polymer systems <2002MM2432, 2002PLM3469, 2005PB237>. Typical examples of... 

Typically, polymers of these acrylic and methacryUc esters are produced as copolymers with other acrylic and vinyl monomers. For example, acrylonitrile is often added to impart additional water and solvent resistance. Other features that can be improved include abrasion resistance, adhesion, elasticity, flexibility and film hardness. Enhanced durability to laundering can be achieved by incorporating reactive, especially crosslinking, monomers such as A -methylol acrylamide, hydroxyethyl acrylate, acrylamide, acrylic and methacrylic acid. Optimisation of polymer properties with the large variety of available monomers leads to near endless combinations of copolymers that are limited only by the imagination of the chemist and by the reality of the cost-efficiency ratio. 

In general, the catalysts have been prepared by methods developed in the 1940s, which involve reduction of H2PtCl6 or KjPtCU with, for example, citrate, base or NaBH4 and can then be used directly, or, more usually, protected with a polymer, typically poly(vinyl alcohol) carbowax 20M or poly(vinylpyrrolidone), a colloidal semiconductor such as Ti02, SrTiOj, ZnO etc., in zeolites or in cyclodextrins. When unprotected, the... 

The dielectric constant of the low-hydroxyl grade of poly(vinyl butyral) (see Figure 2.9) will be calculated in detail as an example. The method used to synthesize poly(vinyl butyral) typically results in the presence of a substantial fraction of unreacted hydroxyl (-OH) groups randomly located on polymer chains. The amount of these hydroxyl groups is normally... 

Among organic dye/polymer systems, hole formation has been reported to take place at 80-120 K for TPP in a phenoxy resin, for a water-soluble TPP in poly(vinyl alcohol), and for TPP in an epoxy resin.25 A typical example of hole formation up to 80 K is shown in Table 2.12 .26 The Arrhenius plot of the quantum efficiency of hole formation, 4>, for TPP in several polymers (Table 2.13 ) shows that 0 gradually decreases at 4-20 K, irrespectively of the nature of the polymer. Above a certain temperature, Tr, 0 decreases markedly, as a result of spectral diffusion and hole filling, attributed to local structural relaxation of the polymer chains. 

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