Polymerization, cationic macromonomer initiators

Polymerization of macromonomers by cationic ring-opening polymerization Macromonomer has been prepared from 2-(p-hydroxyphenyl)-2-oxazoline and ethylene oxide using n-butyl lithium to initiate the anionic polymerization of EO 16I). The living chains were terminated with CH3I or H20 yielding macromonomers with Mn = 1,010 and M = 1,930, respectively ... 

PolyDXL bis-macromonomers were prepared by cationic polymerization of DXL initiated by triflic anhydride, end-capping of the resulting biftmctional living polymers with triethylamine, and nucleophilic substitution of ammonium end groups by a methacrylate anion. ... 

Polyacetals containing polymerizable acrylate groups at both ends were also prepared (but not fully characterized) by cationic polymerization of DXL initiated with triflic anhydride in the presence of HEMA (hydroxyethyl methacrylate). Radical copolymerization of those bis-macromonomers with acrylic acid led to degradable pH-sensitive networks. ... 

The cationic ring opening polymerization of oxolane (THF) or of N-substituted aziridines can be initiated by oxocarbenium salts [42]. The methacrylic ester unsaturation is insensitive to cationic sites, and polyoxolanes (poly-THF) macromonomers are obtained in good yields. 

Macromonomers have been synthesized by living cationic polymerization by three different techniques by the use of a functional initiator, employing functional capping agent or by chain end modification. 

Most of the reported polyfvinyl ether) macromonomers have been prepared with a methacrylate end group which can be radically polymerized and which is non-reactive under cationic polymerization conditions [71-73]. Generally, the synthesis was based on the use of the functional initiator 30, which contains a methacrylate ester group and a function able to initiate the cationic polymerization of vinyl ethers. Such initiator can be obtained by the reaction of HI and the corresponding vinyl ether. With initiator 30 the polymerization of ethyl vinyl ether (EVE) was performed using I2 as an activator in toluene at -40 °C. The MW increased in direct proportion with conversion, and narrow MWD (Mw/Mn= 1.05-1.15) was obtained. The chain length could be controlled by the monomer to initiator feed ratio. Three poly(EVE) macromonomers of different length were prepared by this method Mn=1200,5400, and 9700 g mol-1. After complete... 

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. 

Techniques derived from anionic or cationic living polymerization methods have widely been used. They are efficient because of the long lifetime of the active sites. Once polymerization is completed these sites are used for functionalization purposes. Alternately, unsaturated ionic initiators have been used but to a lesser extent because of the requirement involved that the polymerizable groups remain unscathed during the macromonomer formation. The versatile inifer method has also been applied to the synthesis of macromonomers. 

A class of end-functionalized polymers with polymerizable terminal groups are generally called macromonomers. By both functional initiator and terminator methods, a variety of macromonomers have been synthesized in living cationic polymerization of vinyl ethers, styrenes, and isobutene, as summarized in Table 3 [16,31,147,149-151,155,158-171]. Some of these macromonomers are used in the synthesis of graft polymers (Section VI.C). 

Although there are some limitations on the molecular weights of the linear polymers which may be obtained by this method, AM polymerization offers an attractive, synthetic route for preparation of functional, medium molecular weight polymers by cationic polymerization of oxiranes. As the process involves the extension of the chain of hydroxyl group containing compound used to initiate the polymerization (initiator), the method is especially well suited for preparation of oligodiols (low molecular weight diols as initiators) and macromonomers (for example, hydroxy-ethyl acrylate as initiator) ... 

Several graft copolymers were prepared by copolymerization of macromonomers described in the previous section. Another route-to-graft copolymer is based on conversion of suitable groups along the chain of preformed polymer into species capable of initiating the cationic ringopening polymerization of suitable monomer. Thus, for example, polym-... 

Combination of a living ionic polymerization and a metal-catalyzed radical polymerization also leads to comb polymers, where both the molecular weights of the arm and main-chain polymers are well controlled. PMMA with poly(vinyl ether) arm polymers of controlled molecular weights (C-l) were prepared by the copper-catalyzed radical polymerization of methacrylate-capped macromonomers carrying a poly-(isobutyl vinyl ether), which were obtained by living cationic polymerization with a methacryloxy-capped end-functionalized initiator.428 Comb polymers with... 

More recently, Schubert and coworkers has made tailor made macromonomers bearing oxetane moiety which is cross-linkable in the presence of cationic species [151]. Recently developed ATRP has been recognized as a useful method to polymerize monomers bearing different functionalities such as epoxides in the side chain that could find potential applications in coatings and adhesives. Scheme 11.47 illustrates the preperation of polymers with oxetanes as pendant groups that are preserved through ATRR The resulting polymer is notably cross-linkable when small amount of cationic initiator is supplied. 

Only a few examples of macromonomers prepared cationically have appeared in the literature despite the development of many systems susceptible to living cationic polymerization. Similarly, with all the living procedures the polymerizable end group can be introduced by either functional termination or functional initiation. 

A large variety of macromonomers have also been prepared by cationic polymerization. Basically three major approaches are also valid for the synthesis initiation from functional initiators, end-capping with a heterofimctional deactivator, and a... 

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