Poly copolymers ring-opening polymerization

Poly(tetramethylene oxide) polyols (see Scheme 4.4) are a special class of polyethers syndiesized via acid-catalyzed ring-opening polymerization of tetrahy-drofuran. Although less susceptible to side reactions, the synthesis of these C4 ethers is less flexible in terms of product composition and structure. Thus, because of diis syndietic route, only two-functional glycols are available and copolymers are not readily available. Molecular weights of commercial C4 glycols range up to about 3000 g/m. 

The poly(glycolide-co-caprolactone) (PGCL) copolymer was mainly synthesized by the ringopening polymerization. A copolymer with 1 1 mole ratio was synthesized by the ring-opening polymerization in the presence of the catalyst Sn(Oct)2 by Lee and coworkers. The polymerization was under vacuum, and heated in an oil bath at 170°C for 20 h. The copolymer was then dried under vacuum at room temperature for 72 h. The schematic reaction equations are shown in Schemes 8.5 and 8.6. 

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]. 

Becer CR, Paulus RM, Hoppener S et al. (2008) Synthesis of poly(2-ethyl-2-oxazoline)-h-poly(styrene) copolymers via a dual initiator route combining cationic ring opening polymerization and atom transfer radical polymerization. Macromolecules 41 5210-5215... 

Kinetic measurements of the ring-opening polymerization of trimethylene carbonate (TMC) versus the enchainment of oxetane and CO2 to provide poly (TMC) reveal that these processes in the presence of (salen)CrCl and an ammonium salt have similar free energies of activation (AG ) at 110°C. This similarity in reactivity coupled with the observation that in situ infrared studies of the copolymerization of oxetane and CO2 showed the presence of TMC during the early stages of the reaction has led to the overall mechanism for copolymer production shown in... 

Here we discuss dispersion polymerizations that are not related to vinyl monomers and radical polymerization. The first one is the ring-opening polymerization of e-caprolactone in dioxane-heptane (30). A graft copolymer, poly(dodecyl acrylate)-g-poly(e-caprolactone), is used as a stabilizer. The polymerization proceeds via anionic or pseudoanionic mechanism initiated by diethylaluminum ethoxide or other catalysts. The size of poly(caprolactone) particles depends on the composition of stabilizer, ranging from 0.5 to 5 i,m. Lactide was also polymerized in a similar way. Poly(caprolactone) and poly(lactide) particles with a narrow size distribution are expected to be applied as degradable carriers of drugs and bioactive compounds. 

A kinetic study of the ring-opening polymerization (ROP) of trimethylene carbonate similarly afforded AG at 383 K of 101.9 kj mol-1, a value which was very close in energy to that found for the production of poly(TMC) from oxetane and C02. Hence, based on these experimental findings, the formation of polycarbonate from the oxetane and C02 coupling reaction was shown to occur via two different or concurrent pathways-that is, the intermediacy of TMC formation, and the subsequent polymerization and/or direct enchainment of oxetane and C02 (Figure 8.16). The presence of small amounts of ether linkages in the copolymer also supported this conclusion. 

Poly[(A)-s-(A )-s-(B)] three-arm star-block copolymer Poly[(A)2-s-(B)] three-arm star-block copolymer Poly[(A)2-s-(B)2] four-arm star-block copolymer Poly[(A)-b-(B)-b-(C)] linear triblock copolymer Poly[(A)-s-(B)-s-(C)] three-arm star-block copolymer N,N- Dimethylacetamide Anionic ring-opening polymerization... 

We recently investigated a different route for the synthesis of poly(IB-h-f-CL) diblock and poly( -CL-fo-IB-fo- -CL) triblock copolymers by site-transformation of living cationic polymerization of IB to cationic ring-opening polymerization of -CL via the activated monomer mechanism [95]. 

A similar technique was employed for the synthesis of miktoarm stars having PS, PEO, poly(e-caprolactone) (PCL) or PMMA branches [57]. A PS-h-PMMA diblock copolymer possessing a central DPE derivative, bearing a protected hydroxyl function was prepared. After deprotection and transformation of the hydroxyl group to an alkoxide the anionic ring opening polymerization of the third monomer (EO or e-CL) was initiated. Only limited characterization data were given in this communication. 

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