Macromonomers functionalized

Cationic polymerization has also progressed considerably in the direction of controlled living polymerization. For example, advances have been made in the polymerization of isobutylene and vinyl ethers. These include controlled initiation processes, the use of ini-fers, binifers, trinifers, the preparation of bifunctional monomers, macromonomers, functional monomers and telechelic polymers based on isobutylene and the vinyl ethers. 

Copolymerization of macromonomers formed by backbiting and fragmentation is a second mechanism for long chain branch formation during acrylate polymerization (Section 4.4.3.3). The extents of long and short chain branching in acrylate polymers in emulsion polymerization as a function of conditions have been quantified.20 ... 

Depending on the choice of transfer agent, mono- or di-cnd-functional polymers may be produced. Addition-fragmentation transfer agents such as functional allyl sulfides (Scheme 7.16), benzyl ethers and macromonomers have application in this context (Section 6.2.3).212 216 The synthesis of PEG-block copolymers by making use of PEO functional allyl peroxides (and other transfer agents has been described by Businelli et al. Boutevin et al. have described the telomerization of unsaturated alcohols with mercaptoethanol or dithiols to produce telechelic diols in high yield. 

One of the major advantages of radical polymerization over most other forms of polymerization, (anionic, cationic, coordination) is that statistical copolymers can be prepared from a very wide range of monomer types that can contain various unprotected functionalities. Radical copolymerization and the factors that influence copolymer structure have been discussed in Chapter 7. Copolymerization of macromonomers by NMP, ATRP and RAFT is discussed in Section 9.10.1. 

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),... 

Highly branched polymers, polymer adsorption and the mesophases of block copolymers may seem weakly connected subjects. However, in this review we bring out some important common features related to the tethering experienced by the polymer chains in all of these structures. Tethered polymer chains, in our parlance, are chains attached to a point, a line, a surface or an interface by their ends. In this view, one may think of the arms of a star polymer as chains tethered to a point [1], or of polymerized macromonomers as chains tethered to a line [2-4]. Adsorption or grafting of end-functionalized polymers to a surface exemplifies a tethered surface layer [5] (a polymer brush ), whereas block copolymers straddling phase boundaries give rise to chains tethered to an interface [6],... 

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. 

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. 

Macromonomers generally exhibit low molecular weights (up to 20,000) which allows accurate control of functionalization yield. Careful sample characterization and polydispersity control are necessary to check the efficiency of the synthesis. 

Preparation of macromonomers is generally performed by deactivation of the living sites by an unsaturated electrophile. Again the difficulty is to get quantitative functionalization, and absence of side reactions. Here are a few examples ... 

Polyamide macromonomers can be made by reaction of the terminal acyllactam function with an unsaturated nucleophile such as the anion derived fromp. vinylbenzyl amine 8I). The nucleophilicity of the latter is higher than that of the lactam anion, and the reaction is straightforward. 

The purpose of this review is to show how anionic polymerization techniques have successfully contributed to the synthesis of a great variety of tailor-made polymer species Homopolymers of controlled molecular weight, co-functional polymers including macromonomers, cyclic macromolecules, star-shaped polymers and model networks, block copolymers and graft copolymers. 

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. 

The enzymatic polymerization of 12-hydroxydodecanoic acid in the presence of 11-methacryloylaminoundecanoic acid conveniently produced the methacrylamide-type polyester macromonomer. Lipases CA and CC were active for the macromonomer synthesis. Enzymatic selective monosubstitution of a hydroxy-functional dendrimer was demonstrated. Lipase CA-catalyzed polymerization of 8-CL in the presence of the first generation dendrimer gave the poly(8-CL)-monosubstituted dendrimer. 

Anionic polymerization in suitable systems allows the preparation of polymers with controlled molecular weight, narrow molecular weight distributions and functional termination. The functional termination of a living anionic polymerization with a polymerizable group has been used frequently in the preparation of macromonomers (4). Our research has encompassed the anionic homo and block copolymerizations of D- or hexamethyl cyclotrisiloxane with organolithiums to prepare well defined polymers. As early as 1962 PSX macromonomers were reported in the literature by Greber (5) but the copolymerization of these macromonomers did not become accepted technique until their value was demonstrated by Milkovich and... 

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. 

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

The functionality of the end groups were also determined by NMR or UV analysis which should provide identical molecular weights for perfectly monofunctional materials. As can be seen in Table I, a good correspondence was obtained. Incorporation of the macromonomers into copolymers via free radical copolymerization can also be used as a check on functionality since nonfunctional materials obviously will not be incorporated. Proton NMR was used to confirm the amount of PSX... 

State-of-the-art polymeric materials possess property distributions in more than one parameter of molecular heterogeneity. Copolymers, for example, are distributed in molar mass and chemical composition, while telechelics and macromonomers are distributed frequently in molar mass and functionality. It is obvious that n independent properties require n-dimensional analytical methods for accurate (independent) characterization of the different structural parameters. 

Structural control of polymer terminal has been extensively studied since terminal-functionalized polymers, typically macromonomers and telechelics, are often used as prepolymers for synthesis of functional polymers. Various methodologies for synthesis of these polymers have been developed however, most of them required elaborate and time-consuming procedures. By selecting... 

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. 

PS-fr-PBd) star-block copolymers were synthesized by the macromonomer technique in combination with anionic polymerization and ROMP [ 158], following the procedure outlined in Scheme 83. The macromonomers were prepared with two different methods. In the first the living diblock copolymer was reacted with ethylene oxide to reduce the nucleophihcity of the living end followed by termination with 5-carbonyl chloride bicycle (2.2.1) hept-2-ene, while in the second method the functional initiator 5-lithiomethyl bicycle... 

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