Alcohols ring-opening polymerization

An alcohol could initiate the ring-opening polymerization of lactones by lipase catalyst ( initiator method ). In the lipase CA-catalyzed polymerization of DDL using 2-hydroxyethyl methacrylate as initiator, the methacryloyl group was quantitatively introduced at the polymer terminal, yielding the methacryl-type polyester macromonomer [98]. This methodology was expanded to synthesis of co-alkenyl- and alkynyl-type macromonomers by using 5-hexen-l-ol and 5-hexyn-l-ol as initiator. 

The earliest reported ring-opening polymerizations of functionalized norbornenes were carried out in protic solvents (alcohol, water) using iridium, ruthenium, or osmium salts. Thus, norbornenes substituted with ester (93-95), hydroxy (95), chlorine (96), alkoxy (97), and imide (93) groups have been polymerized via metathesis using noble metal catalysts. 

Moreover, alcohol functionalities have been introduced into the polynor-bornene (PNB) backbone by copolymerization of norbornene with a few percent of 5-acetate norbornene and subsequent acetate reduction. After transformation of the pendant hydroxyl functions into diethyl aluminum alkoxides, sCL has been ring opening polymerized (Scheme 31). Owing to the controlled/ liv-ing character of both polymerization processes the isolated poly(NB- -CL) graft copolymers were characterized by well-defined composition, controlled molecular weight and branching density, and narrow MWD (PDI=1.2-1.4) [92]. 

The first example of a catalytic reaction at the core of dendrimers was provided by Frechet (79) using dendritic alcoholates such as 86 as macro-initiators for anionic ring-opening polymerization of a-caprolactone. Usually the alkali... 

Ring-opening polymerization R-CO-OR (cycUc) Alcohol/water Polyesters [58-81]... 

By organic chemistry formalism, polyacetals are reaction products of aldehydes with polyhydric alcohols. Polymers generated from aldehydes, however, either via cationic or anionic polymerization are generally known as polyacetals because of repeating acetal linkages. Formaldehyde polymers, which are commercially known as acetal resins, are produced by the cationic ring opening polymerization of the cyclic trimer of formaldehyde, viz., trioxane [29-30] (Fig. 1.5). 

Uses. Furfural is primarily a chemical feedstock for a number of monomeric compounds and resins. One route produces furan by decarbonylation. Tetrahydrofuran is derived from furan by hydrogenation. Polytetramethylene ether glycol [25190-06-1] is manufactured from tetrahydrofuran by a ring opening polymerization reaction. Another route (hydrogenation) produces furfuryl alcohol, tetrahydrofurfuryl alcohol, 2-methylfuran, and 2-methyltetrahydrofuran. A variety of proprietary synthetic resins are manufactured from furfural and/or furfuryl alcohol. Other... 

From fluorine-containing Lewis acids, BF3 is most often used as initiator of the cationic ring-opening polymerization. This is at least partly due to the fact that BF3 forms a stable, well-defined complex with ethers (e.g., BF3 Et20, m.p. = -59°C,b.p. = 125° C) [34]. Complexes of BF3 with ethers or alcohols are the commercial products, whereas gaseous BF3, if needed, may be conveniently obtained by thermal decomposition (>100° C) of relatively less stable complex with anisole. 

The problem of water in ionic ring-opening polymerization is much less critical than in vinyl polymerization, because, if present, water in the former system has to compete with relatively nucleophilic monomer present in large excess. Thus, certain polymerizations (e.g., polymerization of cyclic amine-conidine) can be conducted even in alcohols as solvents. 

Cationic polymerization of 1,3,5-trioxane, however, is different from other typical ring-opening polymerizations, because polymer is insoluble in its own monomer or in any typical organic solvent (it may be dissolved however in DMF at —150° C and perfluorinated alcohols at room temperature). Thus, at any polymerization system, already at the early stage of polymerization, polymer precipitates out of solution and further reaction involves active species in crystalline phase. 

The first example of fully aqueous metal catalysis of olefin isomerization was reported by Grubbs et al. in 1994 [2]. These authors adopted [Ru(H20)6](tos)2 (tos = p-toluenesulfonate) [8] as a catalyst, which is highly active for the ring-opening polymerization of strained cyclic olefin. Both allylic alcohol and allylic ethers undergo isomerization in the presence of [Ru(H20)6](tos)2. 

The most widely used catalyst for the stepwise ring-opening polymerization of alkylene oxides is potassium hydroxide. This reaction (KOH catalyst), however, is accompanied by side reactions, e.g., the formation of allyl alcohol brought about by the isomerization of propylene oxide. 

For transesterification of ethyl acetate with various alcohols promoted by mixed organotin oxides, more detailed studies have been carried out on the structure and catalytic properties of supported tin dichloride and trichloride precursors, and on mixed organotin oxides of the type [P—(CH2) —SnBuCl]20. " " It was found that ring opening polymerization of e-caprolactone using the supported mixed organotin oxide, in the presence of propanol, required lengthy spacers (11 carbon atoms was found to be the best) between the polystyrene matrix and tin, in order to avoid the collapse of the resin beads (as observed for a six carbon spacer). The tin contamination could be reduced to <5 ppm in the final products when these types of catalysts were used in the transesterification of ethyl acetate and various alcohols. " ... 

These anionic ring opening polymerizations are usually carried out either in bulk or in solution. A host of catalyst types are active. For synthetic references using specific catalysts, the reader is referred to several excellent sources (4,7,31,32). Representative catalysts include hydroxides, alcoholates, phenolates, silanolates, siloxanolates, mercaptides of the alkali metals, organolithium and potassium compounds, and quaternary ammonium and phosphonium bases and their silanolates and siloxanolates. Some physical characteristics of linear oligomers are given in Table 5 (10). 

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