Vinyl Ether Polymerizable Group

Sodium salt of malonate carbanions are known to react quantitatively with the living ends of poly(vinyl ether)s to give a stable carbon-carbon bond [45]. This reaction was performed to end-functionalize living poly(vinyl ether)s with a vinyl ether polymerizable end group using the functional malonate ion 36 [73,89]. 

Unsaturated tetrahydropyran derivatives have received only cursory attention in the literature as heterocyclic monomers. 2,3-Dihydropyran and several of its substituted derivatives apparently undergo cationic polymerization in a manner typical of vinyl ethers (72MI11103), while tetrahydropyranyl esters of methacrylic acid (123) are fairly typical free radically polymerizable monomers (Scheme 35) (74MI11105). The THP group was used in this study as a protecting group for the acid functionality, and it was found that deprotection of polymers (124) could be accomplished under extremely mild conditions. 

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. 

The pendant functions listed in Figure 3 are often useful and of synthetic interest per se. For example, methacrylate and acrylate esters are polymerizable (cross-linking sites) [19-21] the cinnamate is photorespon-sive (for the photo-induced dimerization of its unsaturated groups) [20] oligo(oxyethylene) [25-27] and carbohydrate groups [35] give hydrophilic and water-soluble polymers, whereas perfluoroalkyl moieties [32-34] enhance hydrophobicity. Thus, poly(vinyl ethers) with cinnamate functions... 

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). 

The polymerizable groups include methacryloyl, styrenic, epoxide, vinyl ether, and others, among which the methacryloyl-capped macromonomers are most widely available from vinyl ethers, styrene, and its derivatives. For example, the a-end methacryloyl group can be introduced by the functional initiator method, with the hydrogen halide-adduct of 2-... 

All cationically polymerizable monomers can be potentially used in this process however, the main study has been focused so far on the most reactive oxirane and vinyl ethers [4], Alkoxysilane derivatives - the most common acid-sensitive monomers for the synthesis of siloxane materials through the use of sol-gel methods - were not used extensively. Only a few examples of their application in photo-activated cross-linking can be noted, mainly in co-reaction with oxirane sites [5]. Typically, alkoxysilanes are subjected to an acid- or base-catalyzed process involving hydrolysis of an =SiOR group and then condensation of the formed silanol with another molecule bearing an =SiOH or =SiOR function to give a siloxane linkage [6]. It was of interest to combine the properties of cross-linked silicone materials with the ones provided by sterically overloaded... 

End-functionalized polymers with polymerizable groups such as double bonds and heterocycles of course provide macromonomers allyl, vinyl ester, vinyl ether, lactone, and epoxy are examples of such a category whose a-ends are not susceptible or have little susceptibility to metal-catalyzed radical polymerization. As discussed above, for example, allyl chloride and bromide (FI-33 and FI-34) are effective initiators to be used for styrene with CuCl and CuBr catalysts,161 while allyl compounds with remote halogens such as FI-35 and FI-36 allow the polymerization of methacrylates with high initiation effi-... 

A review of functional polymers by carbocationic polymerization both with and without the use of protecting groups has recently appeared. Protecting groups have also been employed as cationic coinitiators, cationic terminating agents, and cationic polymerizable monomers. Scheme 2 illustrates the use of protected functional cationic coinitiators for vinyl ether polymerization. 

Real Time (RT-) FTIR spectroscopy pormits not only to follow quantitatively the polymerization by monitoring the disappearance of the IR absorption characteristic of the polymerizable reactive groups (acrylates, methacrylates, epoxy rings, vinyl ether double bonds, thiol groups etc.) but also to determine at any moment the actual degree of conversion and hence the residual imreacted groups content. This analytical method has proved extremely valuable for measuring the polymerization rates and quantum yields of reactions that develop in the millisecond time scale. 

This technique is the simplest as it generally requires only one step as the polymerizable function is incorporated via the initiator fragment. Most macromonomers have been prepared with a methacrylate end group [144-146] which is unreac-tive under cationic polymerization conditions. For instance, the synthesis of the poly(vinyl ether) macromonomer was reported by employing initiator 3, which contains a methacrylate ester group and a function able to initiate the cationic polymerization of vinyl ethers. Other vinyl ethers were also polymerized using initiator 3 under similar conditions [147]. 

Functionalized monomers are sometimes regarded as polymerizable surfactants. Vinyl or allyl monomers are reacted with ethylene oxide (EO), propylene oxide (PO) or butylene oxide (BO) in a sequential or random addition mode. The terminal hydroxyl group can be optionally reacted with methyl or benzyl chloride to produce Williamson ethers (if the hydroxyl group has to be deactivated) or are further sulfated to deliver electrosteric stabilization. 

Zilkha s group also reported a series of papers describing the synthesis of mechanically crosslinked polymer through vinyl polymerization [223-225]. They employed the radical copolymerization of a 32-membered crown ether derivatives having one polymerizable double bond with styrene or methyl methacrylate (Scheme 49). Sufficient chain threading repeatedly took place... 

The intensive development of chelate-type MCMs can be taken into account. Fragmentary data (most often without either quantitative data or study of the reaction mechanism) on radical copolymerizations of MCMs - Schiflf bases with vinyl groups, macrocyclic complexes (hemins, phthalocyanines etc.) - point us in this direction. Probably, polymerizable crown ethers with exocyclic groups and metal ions in the ring (ciyptands, podands etc.) will be synthesized. 

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