Free Radical Polymerization of vinyl monomers

Noda and Watanabe [42] reported a simple synthetic procedure for the free radical polymerization of vinyl monomers to give conducting polymer electrolyte films. Direct polymerization in the ionic liquid gives transparent, mechanically strong and highly conductive polymer electrolyte films. This was the first time that ambient-temperature ionic liquids had been used as a medium for free radical polymerization of vinyl monomers. The ionic liquids [EMIM][BF4] and [BP][Bp4] (BP is N-butylpyridinium) were used with equimolar amounts of suitable monomers, and polymerization was initiated by prolonged heating (12 hours at 80 °C) with benzoyl... 

Active polymers from oligoperoxides. Active polymers can be obtained by the free radical polymerization of vinyl monomers with oligoperoxides as the initia-... 

The rates of radical-forming thermal decomposition of four families of free radical initiators can be predicted from a sum of transition state and reactant state effects. The four families of initiators are trarw-symmetric bisalkyl diazenes,trans-phenyl, alkyl diazenes, peresters and hydrocarbons (carbon-carbon bond homolysis). Transition state effects are calculated by the HMD pi- delocalization energies of the alkyl radicals formed in the reactions. Reactant state effects are estimated from standard steric parameters. For each family of initiators, linear energy relationships have been created for calculating the rates at which members of the family decompose at given temperatures. These numerical relationships should be useful for predicting rates of decomposition for potential new initiators for the free radical polymerization of vinyl monomers under extraordinary conditions. 

Hydrogels can be made by a number of methods, but one of the most widely used methods is free radical polymerization of vinyl monomers. Examples of vinyl monomers used in our laboratory are shown in Table 1. Monomers are crosslinked with divalent monomers such as A,A -methyl-enebisacrylamide. Biodegradable crosslinking agents can also be used as long as they have bifunctionality. 

Tab. 9.2 Specific surface modifications and SAM systems of particles or planar substrates for the surface-initiated free radical polymerization of vinyl monomers. 

Eastmond, G. C., The Kinetics of Free Radical Polymerization of Vinyl Monomers in Homogeneous Solutions, Chap. 1 in Comprehensive Chemical Kinetics, Vol. 14A, C. H. Bamford and C. F. H. Tipper, eds., American Elsevier, New York, 1976a. 

The following experiment describes the background of free radical polymerizations of vinyl monomers. This information will be experimentally illustrated in experiments involving bulk and emulsion polymerizations of styrene. 

GAPDS and AMPH can also be employed, first in the synthesis of the corresponding polypeptide initiators containing -S-S- or N=N groups and then submitted to photolysis, thus giving the free radical polymerization of vinyl monomers (Scheme 48). 

In general, a polymerization process model consists of material balances (component rate equations), energy balances, and additional set of equations to calculate polymer properties (e.g., molecular weight moment equations). The kinetic equations for a typical linear addition polymerization process include initiation or catalytic site activation, chain propagation, chain termination, and chain transfer reactions. The typical reactions that occur in a homogeneous free radical polymerization of vinyl monomers and coordination polymerization of olefins are illustrated in Table 2. 

To illustrate the calculation of molecular weight averages using moment equations, let us consider a free radical polymerization of vinyl monomers. Table 3 shows the kinetic equations based on the kinetic... 

The existence of quinonic groups in carbon black was first proposed by Studebaker and associates (73), based on reduction experiments with sodium borohydride or hydrogen over platinum. Carbon black undergoes some of the typical reactions of quinones. It inhibits the free radical polymerization of vinyl monomers (74—76) and, after completion of the induction period, becomes grafted to the polymer molecules. This activity is lost on reduction. Gruver and Rollmann (77) have shown that quinones are also responsible for some of the antioxidant activity of carbon black (78). Hallum and Drushel (79) proposed that surface quinonic groups... 

Homolytic processes Evidence also has been presented for the radical-induced decomposition of thiolsulfinates (6,7). Homolytic cleavage is facilitated by the weak S-S bond ( 40kcal). The availability of sulfidic sulfur for radical attack is indicated by the observation that thiolsulfinates strongly retard the free radical polymerization of vinyl monomers (8). 

Monomers and Resins. Radiations such as 7 rays, ultraviolet light, and electron beams can initiate free-radical polymerization of vinyl monomers or unsaturated resins. Styrene, vinyl acetate, acrylonitrile, acrylates. 

I Ls containing a chiral cation ora chiral anion have been reported and are thought to play an important role for asymmetric synthesis or for chiral separation (6-9) [32-37]. A chiral IL based on l-((-)-menthoxycarbonylmethylene)-3-mefhylimida-zolium) hexafluorophosphate has been applied in stereospecific free-radical polymerization of vinyl monomers. The asymmetric environment of chiral ILs is believed to have some effect on the stereostructure of polymers [38]. 

It may be noted that a frequently used thermal initiator of free radical polymerization of vinyl monomers, 2,2 azobis (isobutyronitrile) is not suitable for crosslinking... 

Vinyl polymers Thermoplastic Hnear polymers synthesized by free radical polymerization of vinyl monomers having a common structure of CH2=CHR. 

An unusual free-radical polymerization of vinyl monomers utilizes ultrasound to both emulsify monomer and to create free radicals [7]. The ultrasound (at 20 kHz) acts on water to create hydrogen and hydroxyl-initiating radicals, an initiating system that bears resemblance to many radiation-induced polymerizations. The first claimed emulsion polymerizations by ultrasound were those of butyl acrylate and vinyl acetate [7]. In most cases it was observed that the particle... 

Two major types of materials have until now been applied to molecular imprinting, either organic polystyrenes/polyacrylates, or inorganic polysiloxanes. Variations are abundant but these have nevertheless been the most popular, sometimes also used in combination. In this chapter, a survey of building blocks is given and basic synthetic schemes presented. Since organic matrices are by far the more important, organic polymeric systems based on free-radical polymerization of vinyl monomers are exclusively covered. An account on polysiloxane chemistry is covered by Chapter 11 in this volume. 

Different radioactive sources can initiate free-radical polymerizations of vinyl monomers. They can be emitters of gamma rays, beta rays, or alpha particles. Most useful are strong gamma emitters, like to or Sr. Electron beams from electrostatic accelerators are also efficient initiators. The products from irradiation by radioactive sources or by electron beams are similar to, but not identical to, the products of irradiation by ultraviolet light. Irradiation by ionizing radiation causes the excited monomer molecules to decompose into free radicals. Ionic species also form from initial electron... 

The free radical polymerization of vinyl monomers should benefit from the excellent heat transfer and mixing speed of micro-reactors. When Hessel et al. [15] investigated, for the first time, the use of a micro-reactor in a free radical polymerization, they modeled the outcome of a solution polymerization of styrene as a monomer and azobisisobutylonitrile (AIBN) as an initiator for three different micro-reactor types [16], the aim being to compare the effects of micro-reactor... 

In general, the free-radical polymerization of vinyl monomers includes chain initiation, propagation, chain transfer to monomer and bimolecular termination reactions. However, there is strong evidence that, in the free-radical polymerization of VCM, some reactions (e.g., chain transfer to monomer, formation of short- and long-chain branches, etc.) involve complex kinetic mechanisms [44]. In fact, the presence of chloromethyl and ethyl short-chain branches in PVC validates the conclusion that the propagation reactions involve several types of radicals [46]. Figures 4.8—4.10 show in detail the mechanisms leading... 

Simal, R Demonceau, A. Noels, A. F. Highly efficient ruthenium-based catalytic systems for the controlled free-radical polymerization of vinyl monomers. Angew. Chem., Int. Ed. Engl. 1999, 38, 538-540. 

Thus far, oxidoreductases are mostly engaged in polymer synthesis in two major areas. First, they are employed for the polymerization of phenols and anilines. In the former case, the products include polyphenols (39) and polyCphenylene oxide) (40). In the latter case, wata -soIuble polyaniline polymers can be made (41). Secondly, oxidoreductases are employed for the free-radical polymerization of vinyl monomers (42). 

Stereo control can also be achieved in the homogeneous free-radical polymerization of vinyl monomers by varying the polymerization temperature. Some typical monomers that behave in this manner include methyl methacrylate,(39) vinyl acetate,(41) vinyl chloride,(42) isopropyl and cyclohexyl acrylates.(40) As the polymer temperature is lowered the crystallizabiUty of the polymers becomes more discernible. (46) This observation can be attributed to the fact that as the temperature is lowered there is a preference for units in the same configuration to be added to the growing chain. It has been found that in general there is a preference for syndiotactic sequences to develop as the temperature is lowered. As an example, the observed melting temperature of poly(vinyl chloride) increases from 285 °C to 310 °C as the polymerization temperature is lowered from —15 °C to —75°C, with a concomitant increase in the syndiotacticity.(47)... 

---