Emulsion polymerization graft copolymers

The emulsion polymerized graft copolymer, technically more important than the blend copolymer, may be written ... 

Emulsion polymerizations of vinyl acetate in the presence of ethylene oxide- or propylene oxide-based surfactants and protective coUoids also are characterized by the formation of graft copolymers of vinyl acetate on these materials. This was also observed in mixed systems of hydroxyethyl cellulose and nonylphenol ethoxylates. The oxyethylene chain groups supply the specific site of transfer (111). The concentration of insoluble (grafted) polymer decreases with increase in surfactant ratio, and (max) is observed at an ethoxylation degree of 8 (112). 

Compatibilizer ABS copolymers have been prepared via an emulsion polymerization process. These copolymers have been functionalized with glycidyl methacrylate (GMA). The functionalized copolymers are blended PBT. Characterization by thermal mechanical analysis indicates that PBT is partially miscible with ABS and the glycidyl grafted ABS (48). 

ASA structural latexes have been synthesized in a two stage seeded emulsion polymerization. In the first stage, partially crosslinked poly(n-butyl acrylate) and poly( -butyl acrylate-sfaf-2-ethylhexyl acrylate) rubber cores are synthesized. In the second stage, a hard styrene acrylonitrile copolymer (SAN) shell is grafted onto the rubber seeds (16). 

Most ABS is made by emulsion polymerization. A polybutadiene or nitrile rubber latex is prepared, and styrene plus acrylonitrile are grafted upon the elastomer in emulsion. The effect of rubber particle size in ABS graft copolymer on physical properties is the subject Chapter 22 by C. F. Parsons and E. L. Suck. Methyl methacrylate was substituted for acrylonitrile in ABS by R. D. Deanin and co-workers. They found a better thermoprocessability, lighter color, and better ultraviolet light stability. 

We have shown (12, 14) that block and graft copolymers (BG copolymers have emulsifying properties in polymeric oil-in-oil emulsions. ... 

In this review we summarize and discuss the amphiphilic properties of polyoxyethylene (PEO) macromonomers and PEO graft copolymer molecules, the aggregation of amphiphilic PEO macromonomers into micelles, the effect of organized aggregation of macromonomers on the polymerization process, and the kinetics of radical polymerization and copolymerization of PEO macromonomer in disperse (dispersion, emulsion, miniemulsion, microemulsion, etc.) systems [1-5]. 

Thus in the emulsifier-free emulsion copolymerization the emulsifier (graft copolymer, etc.) is formed by copolymerization of hydrophobic with hydrophilic monomers in the aqueous phase. The ffee-emulsifier emulsion polymerization and copolymerization of hydrophilic (amphiphilic) macromonomer and hydro-phobic comonomer (such as styrene) proceeds by the homogeneous nucleation mechanism (see Scheme 1). Here the primary particles are formed by precipitation of oligomer radicals above a certain critical chain length. Such primary particles are colloidally unstable, undergoing coagulation with other primary polymer particles or, later, with premature polymer particles and polymerize very slowly. 

Block or graft copolymers in a selective solvent can form structures due to their amphiphilic nature. Above the critical micelle concentration (CMC), the free energy of the system is lower if the block copolymers associate into micelles rather than remain dispersed as single chains. Often the micelles are spherical, with a compact core of insoluble polymer chains surrounded by a corona of soluble chains (blocks) [56]. Addition of a solvent compatible with the insoluble blocks (chains) and immiscible with the continuous phase leads to the formation of swollen micelles or polymeric micro emulsion. The presence of insoluble polymer can be responsible for anomalous micelles. 

The emulsifier-free emulsion terpolymerization of PEO-MA macromonomer, BA, and acrylic acid (AA) led to the formation of graft copolymers and stable latexes [101]. At the beginning of terpolymerization, the PEO-MA macromonomer polymerized more quickly than BA or AA. Conversion of the macromonomer increased with increasing initiator concentration and with decreasing mo-... 

Wenz and colleagues at Bayer Polymers Inc. describe the use of Raman spectroscopy to monitor the progress of a graft emulsion polymerization process, specifically the manufacture of ABS graft copolymer, in order to select the appropriate reaction termination point.40 Early termination reduces product yield and results in an extra product purification step termination too late reduces product quality. As Figure 5.5 illustrates, the reaction composition over time is not smooth and predictable, making it unlikely that off-line analysis would ever be fast enough to ensure correct control decisions. 

The emulsion polymerization process involves the polymerization of liquid monomers that are dispersed in an aqueous surfactant micelle-containing solution. The monomers are solubilized in the surfactant micelles. A water-soluble initiator catalyst, such as sodium persulfate, is added to the aqueous phase. The free radicals generated cause the dispersed monomers to react to produce polymer molecules within the micellar environment. The surfactant plays an additional role in stabilizing dispersion of the produced polymer particles. Thus, the surfactants used both provide micelles to house the monomers and macroradicals, and also stabilize the produced polymer particles [193,790], Anionic surfactants, such as dodecylbenzene sulfonates, are commonly used to provide electrostatic stabilization [193], These tend to cause production of polymer particles having diameters of about 0.1-0.3 pm, whereas when steric stabilization is provided by, for example, graft copolymers, then diameters of about 0.1-10 pm tend to be produced [790,791]. 

Such hydrophilic macromonomers (DPn=7-9) were radically homopolymer-ized and copolymerized with styrene [78] using AIBN as an initiator at 60 °C in deuterated DMSO in order to follow the kinetics directly by NMR analysis. The macromonomer was found to be less reactive than styrene (rM=0.9 for the macromonomer and rs=1.3 for styrene). Polymerization led to amphiphilic graft copolymers with a polystyrene backbone and poly(vinyl alcohol) branches. The hydrophilic macromonomer was also used in emulsion polymerization and copolymerized onto seed polystyrene particles in order to incorporate it at the interface. 

Use of macromonomers as reactive (copolymerizable) surfactants in heterogeneous systems such as emulsion and dispersion constitutes an increasingly important application in the design of polymeric microspheres, as will be discussed later in Sect. 6. Here the macromonomers copolymerize in situ with some of the substrate comonomers to afford the graft copolymers, the grafts (branches) of which serve as effective steric stabilizers by anchoring their backbone onto the surfaces of the particles. In general, however, the copolymerization reactivities of macromonomers in such systems are not well understood yet. 

Abstract Porous copolymers have been prepared by suspension-emulsion polymerization of divinylbenzene with styrene or some methacrylic monomers di(methacryloyloxymethyl)naphthalene, methacrylic ester of p,p -dihydroxy-diphenylpropane diglycidyl ether, and dimethacrylglycolethylene in the presence and absence of chemically modified fillers (fumed silicas with grafted methyl and silicon hydride groups). The results of investigations of the unfilled and filled polymeric systems by IR and 13C NMR spectroscopies combined with AFM are presented. 

Even in polymer chemistry these species may be of interest since more and more attention is devoted to polymerization in confined volumes, such as micelles, whereby the graft copolymer could first help in the emulsion polymerization of a monomer compatible with the backbone and subsequently act as a surface modifier of the polymer formed (wetting agent, pigment binder, coating binder, antistatic compound, adhesion factor, etc.). 

These advantages (wet rub and gloss) may be attributed to the fact that during the polymerization process, there are formed grafted copolymers of vinyl acetate and the water soluble colloids present in the polymerizing medium. These graft copolymers possess marked surface activity and contribute to the stabilization of the emulsion in which they are formed.. . . ... 

To survey as completely as possible the grafting behavior of EVA copolymers toward various vinyl compounds, our investigations covered the grafting of vinyl acetate, vinylidene chloride, and acrylic and meth-acrylic esters. As polymerization processes, at first we preferred suspension polymerization to exclude the influence of solvents by terminating or transfer reactions during polymerization. Grafting by emulsion polymerization, in which the EVA copolymer was dissolved in the monomer before polymerization, was difficult because coagulate was formed as polymerization proceeded. 

In the industrial production of structured AN-Bu-St (ABS) latex particles, the grafting copolymerization of AN and St on crossUnked polybutadiene (PB) seed latex is carried out in emulsion polymerization. Therefore, information on the effect of PB crosslinking density on the swelling of PB latex particles by a St-AN monomer mixture is very important for the production of ABS copolymers with desired properties. Mathew et al. [177] studied the effect of several thermodynamic parameters, such as the crosslinking density, particle size and monomer mixture composition on the swelling behavior of PB latex particles by pure St and AN, and St-AN mixtures of various compositions. They reported... 

Some two stage emulsion graft copolymer materials synthesized and characterized by DMS include) the series poly (methyl methacrylate)/poly(n-butyl acrylate) (PMMA/ PnBA) synthesized by Dickie (14) and the series poly(ethyl methacrylate)/poly(n-butyl acrylate) (PEMA/PnBA) synthesized by Sperling et al. (1) The present study will continue the development of the PEMA/PnBA damping materials by incorporating a common comonomer) ethyl acrylate (EA)) in both stages of the emulsion polymerization. 

In addition to blending with SPMI copolymers, PMI can be incorporated into ABS using mass, emulsion [46-50] or suspension [42] free radical polymerization techniques. The high heat ABS resin can be completely produced by mass polymerization, or mass polymerized PMI-SAN can be blended with (emulsion polymerized) SAN-grafted rubber concentrates and/or conventional mass ABS. Sumitomo Naugatuck determined an empirical relation for the compatibility of SAN/SAN-PMI blends based on the polar monomers in each component [51]. Figure 15.4 shows that the miscibility window with SANs becomes wider with increasing PMI level in the terpolymer [52]. 

Emulsion polymerization has become an important process for the production of a large number of industrial polymers in the form of polymer colloids or latexes. They are the base of adhesives, paints and especially of waterborne coatings. An interest has been developed in recent years in emulsion polymerization systems in which the classical low molecular weight surfactaints are replaced by polymeric surfactants, either hydrophilic-hydrophobic block and graft copolymers (1-4) or functionalized oligomers (5). 

Styrene is frequently used as part of some terpolymers with large practical utilization. One such copolymer is acrylonitrile-butadiene-styrene terpolymer (ABS). Usually it is made as poly(l-butenylene-graft-l-phenylethylene-co-cyanoethylene). This form of the copolymer can be made by grafting styrene and acrylonitrile directly on to the polybutadiene latex in a batch or continuous emulsion polymerization process. Grafting is achieved by the free-radical copolymerization of styrene and acrylonitrile monomers in the presence of polybutadiene. The degree of grafting is a function of the 1,2-vinyl content of the polybutadiene, monomer concentration, extent of conversion, temperature and mercaptan concentration (used for crosslinking). The emulsion polymerization process involves two steps production of a rubber latex and subsequent polymerization of styrene and acrylonitrile in the presence of the rubber latex to produce an ABS latex. 

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