Polymer modification vinyl

Etee-tadical reactions ate accompHshed using a variety of processes with different temperature requirements, eg, vinyl monomer polymerization and polymer modifications such as curing, cross-linking, and vis-breaking. Thus, the polymer industries ate offered many different, commercial, organic peroxides representing a broad range of decomposition temperatures, as shown in Table 17 (19,22,31). 

Deliberate production of (vinyl)polystyrene from (toluenesul-foxyethyl)polystyrene or (haloethyl)polystyrenes was best accomplished by quaternization with N,N-dimethylaminoethanol, followed by treatment with base beta-deprotonation is encouraged in the cyclic zwitterionic intermediate. Reaction was faster and cleaner than with other reagents recommended (64, 76, 77) for eliminations, such as alkoxide, diazabicycloundecene or quaternary ammonium hydroxide this new and efficient procedure may find application elsewhere. Hydrometallation or other additions to polymer-bound olefin may prove useful steps in future syntheses by polymer modification. 

PVA Formation Reaction. Poly(vinyl alcohol) is itself a modified polymer being made by the alcoholysis of poly(vinyl acetate) under acid or base catalysis as shown in Equation 1 (6.7). This polymer cannot be made by a direct polymerization because the vinyl alcohol monomer only exists in the tautomeric form of acetaldehyde. This saponification reaction can also be run on vinyl acetate copolymers and this affords a means of making vinyl alcohol copolymers. The homopolymer is water soluble and softens with decomposition at about 200°C while the properties of the copolymers would vary widely. Poly(vinyl alcohol) has been widely utilized in polymer modification because ... 

The synthesis of poly(vinyl acetals) (252) represents another example of generating a heterocycle, in this case the 1,3-dioxane nucleus, by application of a polymer modification reaction. Generally, the polymer modified is poly(vinyl alcohol) (180) or one of its copolymers. The 1,3-dioxane ring is generated (Scheme 122) by an acid-catalyzed acetalization reaction with an aldehyde, although ketones have also been reacted. A review (71MI11102) is available covering synthesis, properties and applications of the two most common and industrially important poly(vinyl acetals), poly(vinyl butyral) and poly(vinyl formal), as well as many other functional aldehydes that have been attached. 

It has been shown that tensile shear and peel strength for several latex polymers (ethylene vinyl acetate, polyvinyl alcohol, ethylene vinyl chloride, polyvinyl chloride, and acrylic) can be significantly increased by the addition of 10 percent by weight of an epoxy emulsion cured with a tertiary amine curing agent.17 The epoxy modification improves the bond strength in all cases. The degree of improvement is dependent on the selection of the latex type and the chemistry of the latex polymer. 

This modification is connected with a reversed use of the silane (siloxane) coupling agents. On the other hand, the hydrosilylation reaction is commonly applied as a method of crosslinking organic polymers containing vinyl and allyl groups with siloxanes and polysiloxanes with Si-H functionality (e. g., [27]). 

The fundamental theory of phase transfer catalysis (PTC) has been reviewed extensively. Rather than attempt to find a mutual solvent for all of the reactive species, an appropriate catalyst is identified which modifies the solubility characteristics of one of the reactive species relative to the phase in which it is poorly solubilized. The literature on the use of PTC in the preparation of nitriles, halides, ether, and dihalocarbenes is extensive. Although PTC in the synthesis of C- and 0-alkylated organic compounds has been studied, the use of PTC in polymer synthesis or polymer modification is not as well studied. A general review of PTC in polymer synthesis was published by Mathias. FrecheE described the use of PTC in the modification of halogenated polymers such as poly(vinyl bromide), and Nishikubo and co-workers disclosed the reaction of poly(chloromethylstyrene) with nucleophiles under PTC conditions. Liotta and co-workers reported the 0-alkylation of bituminous coal with either 1-bromoheptane or 1-bromooctadecane. Poor 0-alkylation efficiencies were reported with alkali metal hydroxides but excellent reactivity and efficiencies were found with the use of quaternary ammonium hydroxides, especially tetrabutyl- and tetrahexylammonium hydroxides. These results are indeed noteworthy because coal is a mineral and is not thought of as a reactive and swellable polymer. Clearly if coal can be efficiently 0-alkylated under PTC conditions, then efficient 0-alkylation of cellulose ethers should also be possible. 

It is often desirable to perform some kind of chemical modification to polymers once they have formed. Acetylation of cellulose, for example, represents the chemical modification of a naturally occurring polymer (see chapter 3) to give the technologically useful cellulose diacetate and triacetate polymers. Poly(vinyl alcohol) (PVA) is a well-known example of a polymer that can only be formed by chemical modification since vinyl alcohol monomer does not exist (except as its keto form, acetaldehyde). Instead, PVA is formed by hydrolysis of poly(vinyl acetate) (PVAc). Partly hydrolysed PVAc is, of course, simply a copolymer of VA and VAc. As another example, ethylene/vinyl chloride copolymers can be prepared by reductive elimination of chlorine from poly (vinyl chloride) (PVC). The driving force here is that, although ethylene and vinyl chloride can be copolymerised directly, the normal routes to these polymers give insufficient control over composition and sequence distribution. 

These polymers have one vinyl group as the end group which can be utilized for polymer modification by a new chain-growth process. 

This method of classification is useful for pure polymer samples without significant modification or in the absence of additives. In the presence of a polymer modification or blended additives, a misinterpretation may result because of interference from other components. Usually the amounts of additives used in a formulated product are relatively low, and their presence is seldom a major interference. An exception is experienced with certain plasticizers, in which the concentration is often high. A common example is plasticized poly(vinyl chloride), which is a mixture of poly(vinyl chloride), a stabilizer, and a plasticizer such as dioctyl phthalate (often diisooctyl isomer). In this example, features associated with the plasticizer dominate the infrared spectrum. Certain additives, such as fillers (calcium carbonate, for example) may also be misleading, and can confuse the spectral interpretation. For example, products fabricated from poly(vinyl chloride) are used for construction and piping, and these are typically formed from a blend of poly(vinyl chloride) and calcium carbonate. The two examples provided are the common cases where the additives dominate the infrared spectra, and these are sufficiently popular combinations that the spectra are easily recognized. 

Figures 3.8 and 3.9 show a comparison of the various modifications and original PC-SAFT for VLB in the systems polystyrene-propyl acetate (Figure 3.8) and polypropylene-diisopropyl ketone (Figure 3.9). In general, PC-SAFT and simplified PC-SAFT performed similarly, as can be seen from Table 3.16, which gives the errors in prediction for a large number of polymer-solvent VLB systems. Figure 3.10 is a pressure-weight fraction diagram (VLB) for the polymer poly(vinyl acetate) in the associating solvent 2-methyl-l-propanol. A small value of the binary interaction parameter correlates the data well.

MODIFICATION OF PECULIARITIES OF MICROCRYSTALLINE CELLULOSE (MCC) AND ITS OXIDIZED LORM (DIALDEHYDE CELLULOSE DAC) GUANIDINE-CONTAINING MONOMERS AND POLYMERS OF VINYL AND DIALLYL SERIES... 

Polyaniline-montmorillonite nanocomposites were prepared without surface modification of montmorillonite [42]. The polymer nanocomposite was significantly more thermally stable when compared to the pure polymer. Ethylene-vinyl acetate copolymer-clay nanocomposites apparently thermally degrade by a different mechanism than the pure polymer [43]. These observations are consistent with the above thesis. 

Alternately, the acetal-protected polymers have also been prepared by chemical modification on poly(vinylphenol) by reacting the polymer with vinyl ethers using PFTS as the catalyst. ile satisfactory results were obtained with chemical modification using methyl vinyl ether, the reaction with vinyl phenyl ether showed a low efficiency of blocking the phenolic groups as FT-IR studies indicated that the chemically modified polymer still showed some unprotected... 

Poly(vinyl chloride). PVC is one of the most important and versatile commodity polymers (Table 4). It is inherently flame retardant and chemically resistant and has found numerous and varied appHcations, principally because of its low price and capacity for being modified. Without modification, processibiUty, heat stabiUty, impact strength, and appearance all are poor. Thermal stabilizers, lubricants, plasticizers, impact modifiers, and other additives transform PVC into a very versatile polymer (257,258). 

Complexation of the initiator and/or modification with cocatalysts or activators affords greater polymerization activity (11). Many of the patented processes for commercially available polymers such as poly(MVE) employ BE etherate (12), although vinyl ethers can be polymerized with a variety of acidic compounds, even those unable to initiate other cationic polymerizations of less reactive monomers such as isobutene. Examples are protonic acids (13), Ziegler-Natta catalysts (14), and actinic radiation (15,16). 

Modifications of epichlorohydrin elastomers by radical-induced graft polymeri2ation have been reported. Incorporated monomers include styrene and acrylonitrile, styrene, maleic anhydride, vinyl acetate, methyl methacrylate, and vinyHdene chloride (81), acryHc acid (82), and vinyl chloride (81,83,84). When the vinyl chloride-modified epichlorohydrin polymers were used as additives to PVC, impact strength was improved (83,84). 

It may also be mentioned that a number of commercial polymers are produced by chemical modification of other polymers, either natural or synthetic. Examples are cellulose acetate from the naturally occurring polymer cellulose, poly(vinyl alcohol) from polyfvinyl acetate) and chlorosulphonated polyethylene (Hypalon) from polyethylene. 

As with poly(vinyl alcohol), poly(vinyl cinnamate) is prepared by chemical modification of another polymer rather than from monomer . One process is to treat poly(vinyl alcohol) with cinnamoyl chloride and pyridine but this is rather slow. Use of the Schotten Baumann reaction will, however, allow esterification to proceed at a reasonable rate. In one example poly(vinyl alcohol) of degree of polymerisation 1400 and degree of saponification of 95% was dissolved in water. To this was added a concentrated potassium hydroxide solution and then cinnamoyl chloride in methyl ethyl ketone. The product was, in effect a vinyl alcohol-vinyl cinnamate copolymer Figure 14.8)... 

Perhaps the most thoroughly investigated approach is the modification of preformed polymers in particular poly(vinyl isocyanate) and polyacrylonitrile Figure 29.21). 

---