MACROMER copolymerization

We shall continue this study, attempting to Increase the epoxy end group content of the macromer. Capping agents other than ethylene oxide and other terminating agents will be explored. Macromer copolymerizations with propylene oxide or epichlorohydrin will be explored, attempting to prepare polyether type thermoplastic elastomers and hot-melt adhesive. 

The best test for functionality would be in a copolymerization study. A polystyrene with a methacrylate terminal functional group was prepared. A review of relative reactivity ratios indicated that vinyl chloride reacts very rapidly with methacrylates. Therefore, a copolymerization of the polystyrene terminated with a methacrylate functional group in vinyl chloride would be a good test case, and one should observe the disappearance of the MACROMER if the reaction is followed by using GPC analysis. 

The very sharp peak on the left is the MACROMER and the curves on the right are the growing copolymer peaks. One sees that by the time 55% of the vinyl chloride conversion is completed that the MACROMER is virtually completely copolymerized and that its peak has almost disappeared. This at least indicates the existence of a functional MACROMER . 

It was demonstrated that MACROMER will copolymerize with conventional monomers in a predictable manner as determined by the relative reactivity ratios. The copolymer equation ... 

A polystyrene with a functionality such as a methacrylate group copolymerized with a mixture of ethyl and butyl acrylate should yield a graft structure meeting the criteria of a thermoplastic elastomer as shown in Figure 13. The data in this figure show that as the MACROMER content is increased, the tensile... 

The side chains are of a predetermined size and composition via anionic chemistry and based on the reactivity placed at the terminus of the MACROMER and the comonomer with which it will be reacted. The number of side chains per backbone and a distance apart can be reasonably estimated. This distance between side chains must be sufficient that the backbone can manifest its Tg. Considering the earlier comments of molar concentration of the MACROMER in a typical copolymerization recipe, there will not be many MACROMERS per backbone on a statistical basis. 

Peptidyl macromers, in which a vinyl group was introduced at the N-terminus, were synthesized by solid-phase methodology. More specifically, the peptide H-Gly-Gly-Gly-Arg-Gly-Asp-Ser-Pro-OH had acrylic acid coupled to the N-terminus. The peptidyl macromer was cleaved and deprotected by standard methods. Copolymers of styrene with these peptidyl macromers were prepared by radical copolymerization in DMF soln. Cast films were prepared from a CHC13 soln of copolymers. 

The preparation of prepolymers [111] or macromers with functional end groups, so called telechelic polymers, is another approach to structurally unconventional architecture. The functional end groups are introduced either by functional initiation or end-capping of living polymers, or by a combination of the two. In this way, monomers that are not able to copolymerize can be incorporated in a copolymer. Telechelic prepolymers can be linked together using chain extenders such as diisocyanates [112]. In this process, it is essential that the structure and end groups of the prepolymers can be quantitatively and qualitatively controlled [113]. 

Choi et al. [53] have successfully used both water-soluble and oil-soluble initiators in the miniemulsion polymerization of styrene. Alducin and Asua [119] have studied the MWD of polystyrene miniemulsion polymerized with oil-soluble initiators. Rodriguez et al. [61] have developed a mathematical model of seeded miniemulsion polymerization with oil-soluble initiator. Blythe et al. [ 120] have successfully carried out miniemulsion polymerization of styrene with AMBN (oil-soluble). Ghazaly et al. [117] have used AIBN for the miniemulsion copolymerization of a hydrophobic bifunctional macromer. The polymerization progressed much faster when KPS was used than when AIBN was used. This may be due to the tendency of oil-soluble initiator radicals to recombine before initiating polymerization, as discussed by Luo. 

The copolymerization is performed in solution with radical-forming initiators at temperatures of about 70 °C. The silicone macromer contains polymerizable vinyl groups on both chain ends. Such silicone macromers are produced by Wacker GmbH and are available with different chain lengths. The copolymerization with vinyl acetate is very facile and take place statistically [2] after polymerization, no double bonds can be found. To avoid crosslinking, the molecular weight has to be adjusted by the use of chain transfer agents or by the solvent and its concentration. 

An elegant alternative to living polymerization for the preparation of block polymers is to use functionalized Grignard initiators. The polymerization of methyl methacrylate to isotactic (in toluene at — 78"C) or syndiotactic polymers (in THF at — llO C) can be initiated by o-, m-, and p-vinylbenzylmagnesium chloride. The polymers had a low polydispersity and contained one vinylbenzyl group at the chain end, by H-NMR. The poly(methylmethacrylate) macromers thus obtained were polymerized or copolymerized with styrene to give graft and block polymers of controlled architecture [50,51]. 

Macromers by Controlled Initiation. New and unique graft copolymers can be prepared by copolymerizing macromers (macromolec-ular monomers) with conventional monomers. The synthesis of poly(butyl acrylate- -isobutylene), i.e., the first graft synthesis that involves carbocationic controlled initiation, has recently been accomplished by the following route (9) ... 

The copolymerization of the polyisobutenylstyrene macromer with methyl methacrylate and styrene gave further interesting new materials (10,11). 

The monomer reactivity ratios of conmonomers In the copolymerization with styryl type macromer are shown In Table III. Macromers seem to have similar reactivity with ordinary monomer In copolymerization. (13-15)... 

Table III. Monomer Reactivity in the Copolymerization of Polysiloxane Macromers...

LCB [40,41,52,407,522-525]. Both metallocene and Phillips catalysts are thought to produce LCB through macromer insertion, that is, the vinyl end-group on one chain becomes copolymerized into another chain. 

Like metallocenes, Phillips catalysts are usually thought to generate LCB through macromer incorporation [531,532]. The liberated vinyl end-group of one terminated chain is thought to become copolymerized into another... 

An alternate route to graft copolymers is by synthesis of macromolecules possessing exactly one polymerizable group in the chain and their subsequent polymerization, i.e. grafting through. Such reactive polymers are macromolecular monomers, i.e. Macromers as abbreviated by Milkovitch 159), who was the first to call the attention of the scientific community to the importance of this field although macromonomers have been prepared and copolymerized as early as 1962 160). 

LCB results from the copolymerization of ethylene or propene with vinyl-terminated polymer formed during the polymerization. Since vinyl double bonds are more reactive in copolymerization than other types of double-bond end groups, LCB is increased under conditions that generate higher vinyl contents. This can be accomplished by choice of initiator and reaction conditions. Tandem polymerization is also useful, such as by using two initiators, one of which produces a vinyl-terminated oligomer (referred to as a macromonomer or macromer) [Komon and Bazan, 2001 Quijada et al., 2001 Wang et al., 2000]. 

Kim and colleagues copolymerized a number of PECs with oligomers of d/-lactic acid and terminated the resulting copolymer with an acrylate group to form photopolymerizable macromers. The resulting crosslinked polymers were evaluated as biodegradable lubricants for stainless steel needles and a potential substitute for the nonabsorbable silicones used presently. 

A. Koprululu, A. Onen, I. E. Serhatli and F. S. Guner, Synthesis of triglyceride-based urethane macromers and their use in copolymerization . Prog Org Coat, 2008, 63, 365-71. 

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