Macromonomers methacrylate-functionalized

Surprisingly, after this very first example, there was a 20 year delay in the literature in the appearance of the second report on siloxane macromonomers. However, during this period there have been numerous studies and developments in the vinyl and diene based macromonomers91 -94). The recent approach to the synthesis of siloxane macromonomers involves the lithiumtrimethylsilanolate initiated anionic polymerization of hexamethyltrisiloxane in THF 95,123). The living chain ends were then terminated by using styrene or methacrylate functional chlorosilanes as shown in Reaction Scheme X. 

Figure 1. OV spectrum of methacrylate functional PSX macromonomer with M 1600.

A second test was done by using butyl acrylate as the comonomer as shown in Figure 11. The reactivity ratios in this case are such that the methacrylate functionality would react slower with acrylates than with vinyl chloride. As predicted the butyl acrylate is at 62% conversion before the MACROMER peak is significantly diminished. These data add validity to the hypothesis that the placement of side chains in the backbone is dependent on the terminal group of the macromonomer and the relative reactivity of its comonomer. 

A similar procedure was also used for the synthesis of methacrylate functional poly(a-MeS) [80]. Thus, 31 was used in conjunction with SnBr4 in CH2C12 at -78 °C, to obtain the macromonomer with Mns substantially (-50%) higher than the theoretical value. This was probably due to the formation of terminated low MW oligomers with indanyl end group structure. The eliminated proton was as-... 

P-Pinene which is a main component of natural turpentine can be polymerized by living cationic isomerization polymerization [82] (Scheme 10) using TiCl3(OfPr) as a Lewis acid in conjunction with rc-Bu4NCl in CH2C12 at -40 °C. When initiator 31 was used, polymerization led to a poly(P-pinene) macromonomer with a methacrylate function at the a end and a chlorine atom at the co chain end [83]. Three macromonomers were prepared with DPn=8,15, and 25 respectively they had narrow MWD (Mw/Mn= 1.13-1.22) and the reported functionality was close to 1 (Fn=0.90-0.96). 

Well-defined macromonomers of poly(BVE), poly(IBVE), and poly(EVE) with co-methacrylate end group [91] were prepared by living cationic polymerization of the corresponding monomers initiated by trifluoromethanesulfonic add in CH2C12 at -30 °C in the presence of thiolane as a Lewis base. After complete conversion, the polymers were quenched with 37 in the presence of 2,6-lu-tidine or with 41 to produce macromonomers with Mn up to 10,000 g mol-1, with narrow MWD, bearing one polymerizable methacrylate function per molecule. The same polymers were also quenched with 38 in the presence of 2,6-lutidine to give poly(vinyl ether)s with an allylic terminal group. 

Macromonomers with two methacrylate functionalities (MA-PIB-MA) at both ends of the PIB chain have also been synthesized, by a procedure essentially identical to that reported above, but starting with a bifunctional initiator in the polymerization of IB [103]. Free radical copolymerization of the resulting MA-PIB-MA with 2-(dimethylamino)ethyl methacrylate resulted in amphiphilic networks, with a wide range of mechanical and swelling properties. 

High conversion of double bonds was found only with Glissopal, but it was necessary, even in this case, to separate from non-functional PIB before esterification. While the feasibility to synthesize methacrylate functional PIBs by all three methods was demonstrated, due to the necessary column chromatography step to obtain high functionality PIB macromonomers, the utility of the method is questionable. 

Monomethacrylate-functionalized POSS reagents are capable of being polymerized into novel linear silsesquioxane-based materials. Efforts to copolymerize these methacrylate-functionalized POSS with other acryhc comonomers have been successful [96,112]. In a typical polymer synthesis, a 0.5 M toluene solution of macromonomer was prepared, to which 2,2 -azobis(iso-butyronitrile) (AIBN) based on macromonomer was added from a stock solution. The clear solution was heated at 60 °C for 24 h and then precipitated into methanol. Further purification was performed by reprecipitation from toluene into methanol to yield white powder. 

We realized a similar result with dimethylaminoethyl methacrylate as the monomer. Telomerization was performed with 2-mercaptoethanol in the presence of AIBN. This study represents the first example of telomerization of a monomer with a tertiary amine. We showed that the telomerization of such a monomer was highly dependent on the solvent. Indeed, polar solvents strongly favor the nucleophilic addition of thiol onto the methacrylate double bond [255] (Scheme 51). In a second step, oligomers bearing an alcohol group at the chain end can react with IEM to lead to a macromonomer with a methacrylic function. 

Another monomer frequently used is methyl methacrylate. Functional termination is the most common method for the preparation of macromonomers. MMA macromonomers with methacryloyl end groups were prepared [113] according to the following reaction series (Scheme 40). 

Methacrylate functional PIB macromonomers have been synthesized by Hv-ing carbocationic polymerization of IB using the 3,3,5-trimethyl-5-chloro-l-hexyl methacrylate (6)/TiCl4 initiating system in hexane/MeCl 60/40 (v/v) [110, 150]. By varying the monomer to initiator ratio, PIBs in the molecular weight range of 2000-40 000 g moU were obtained with narrow MWDs and close to theoretical ester functionality. 

Apart from the nse of a polymerizable alkoxysilane, silica/polystyrene composite particles with a raspberry-like morphology have been elaborated in the presence of a methyl methacrylate-terminated polyethylene glycol macromonomer. This macromonomer is mainly hydrophilic due to the presence of ethylene oxide repeat units (n 23), which are able to form hydrogen bonds with the silanol groups of silica and adsorb on its snrface. In addition, this molecnle contains a methacrylate functionality able to copoljmerize with styrene thus... 

ATRP has been also used in the grafting-through process using h5nper-branched polyethylene macromonomers with methacrylate functionality prepared by the living Pd-mediated process (164). 

Branched copolymers have also been synthesized by the preparation of macromonomers. Various types of methacrylate-functionalized macromonomers have been reported in the literature for the preparation of graft and star copolyesters. The reaction scheme used for the preparation of the macromonomers is depicted in Figure 4.11. 

Percec and coworkers [184] utilized a similar strategy for the conversion of perfluorinated alkylene functionalized 3,4,5-trihydroxy benzoic acid-type dendrons into methyl methacrylate functionalized dendritic macromonomers. Characterization of the resulting linear-dendritic architectural copolymers involved DSC, x-ray diffraction, and thermal optical polarized microscopy. It was concluded that the self-assembly of the pendant dendritic mesogens forced the linear backbone into a tilted, helical ribbon-type structure. The self-assembly behavior was largely controlled by the multiplicity, composition, and molecular weights of the pendant dendritic mesogens. 

It should be noted that these differ from the more usual macromonomers in that they arc derivatives of methacrylates, a-methylstyrene, mcthacrylonitrile or methacrylamides in which the polymer chain is attached to the a-methyl substituent. In the more common macromonomers terminated with an acrylate or methacrylate function, the polymer chain is part of the ester group, as shown in 2, and in those that contain a st3nyl end group, the chain is usually attached to the aromatic ring, e.g. 3. 

Xi and co-workers [52] prepared methacrylate-functionalized dendritic macromonomers by conversion of the hydroxymethyl group of the polyether dendron to the corresponding bromide and then functionalization with methacrylic acid. Free-radical polymerization of the macromonomer corresponding to a second-generation dendron resulted in formation of a relatively low molecular weight product (X = 6-7). 

A side reaction in NMP is loss of nilroxide functionality by thermal elimination. This may occur by disproportionation of the propagating radical with nitroxide or direct elimination of hydroxy lam ine as discussed in Section 9.3.6.3. In the case of methacrylate polymerization this leaves an unsaturated end group.1" The chemistry has also been used to prepare macromonomers from PMMA prepared by ATRP (Section 9.7.2.1),... 

Recently it has been shown that anionic functionalization techniques can be applied to the synthesis of macromonomers — macromolecular monomers — i.e. linear polymers fitted at chain end with a polymerizable unsaturation, most commonly styrene or methacrylic ester 69 71). These species in turn provide easy access to graft copolymers upon radical copolymerization with vinylic or acrylic monomers. 

Terminal-functionalized polymers such as macromonomers and telechelics are very important as prepolymer for construction of functional materials. Single-step functionalization of polymer terminal was achieved via lipase catalysis. Alcohols could initiate the ring-opening polymerizahon of lactones by lipase catalyst. The lipase CA-catalyzed polymerizahon of DDL in the presence of 2-hydroxyethyl methacrylate gave the methacryl-type polyester macromonomer, in which 2-hydroxyethyl methacrylate acted as initiator to introduce the methacryloyl group quanhtatively at the polymer terminal ( inihator method ).This methodology was expanded to the synthesis of oo-alkenyl- and alkynyl-type macromonomers by using 5-hexen-l-ol and 5-hexyn-l-ol as initiator, respechvely. 

In our own research, the functional termination of the living siloxanolate with a chlorosilane functional methacrylate leading to siloxane macromonomers with number average molecular weights from 1000 to 20,000 g/mole has been emphasized. Methacrylic and styrenic monomers were then copolymerized with these macromonomers to produce graft copolymers where the styrenic or acrylic monomers comprise the backbone, and the siloxane chains are pendant as grafts as depicted in Scheme 1. Copolymers were prepared with siloxane contents from 5 to 50 weight percent. 

End-functional polymers were also synthesized by lipase-catalyzed polymerization of DDL in the presence of vinyl esters [103,104]. The vinyl ester acted as terminator ( terminator method ). In using vinyl methacrylate (12.5 mol % or 15 mol % based on DDL) and lipase PF as terminator and catalyst, respectively, the quantitative introduction of methacryloyl group at the polymer terminal was achieved to give the methacryl-type macromonomer (Fig. 12). By the addition of divinyl sebacate, the telechelic polyester having a carboxylic acid group at both ends was obtained. 

Poly(methyl methacrylate)-g-poly(dimethylsiloxane) copolymers have been prepared by free radical copolymerizations of acrylate-functional siloxane macromonomers (29) with methyl methacrylate. Siloxane macromonomers (29) of between 1,000 and 20,000 molecular weight were utilized to give a range of copolymers with between 4 and 17 wt% silicone115. 

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