Search

Phenoxycarbonyloxymethyl ethylene carbonate 4 was synthesized from glycerol carbonate and phenyl chloroformate Polyurethanes with pendant hydroxyl greups were obtained from polycondensation reactions of this AA* monomer with diamines. These polymers contan primary as well as secondary hydroxyl groups The obtained polyurethanes are amorphous materials. The glass transition temperature decreases with increasing number of methylene groups between the urethane groups.

The cationic bridged zirconocene complex, [iPr(Cp)(InD)Zr(Me)(THF)][BPh 4 ] (1-BPh 4 ) was synthesized. Polymerization of methyl methacrylate with 1-BPh 4 in CH 2 Cl 2 at temperatures between -20 and 20°C led to the formation of isotactic poly(mehtyl methacrylate). The low polydispersity index of the polymer obtained and a successfull two step polymerization of methyl methacrylate with 1-BPh 4 are hints towards a living polymerization mechanism. 1 H and 13 C NMR analysis revealed an enantiomorphic site-controlled mechanism for the formation of isotactic poly(methyl methacrylate).

This review covers most of the authors' work on ring-opening polymerization and copolymerization of heterocyclic monomers during the time of their cooperation since 1985. The mechanistic aspects of anionic ring opening polymerization of cyclic carbonates with a variety of functional groups are described first. By sequential polymerization of first styrene, methyl methacrylate or suitable heterocyclic monomers and then secondly a cyclic carbonate, the site transformation is highlighted. The influence of the chemical nature of macroinitiators with identical active sites on the course of polymerization of cyclic carbonates was studied for poly(ethylene oxide), poly(tetrahydrofuran), and poly(dimethylsiloxane) macroinitiators. For the copolymerization of cyclic carbonates with lactones and lactide the dependence of the polymer microstructure on the polymerization conditions is discussed on the basis of the copolymerization mechanism. The copolymerization of cyclic carbonates with e-caprolactam and with tetramethylene urea results in an alternating copolymer, i. e. a poly(ester urethane) and an [m, n]-polyurethane, respectively, the key step being the insertion of the lactam or the cyclic urea into the carbonate chain. The cationic ring opening polymerization of cyclic six and seven membered carbamates leading to [4]- and [5]-polyurethane with uniform microstructure is reported with respect to kinetic, mechanistic, and thermodynamic aspects. This new access to [n]-polyurethanes by a chain growth reaction allows the synthesis of well defined polymer architectures with polyurethane sequences. Sequential polymerization of tetrahydrofuran and the cyclic carbamate with mono- and bifunctional initiators leads to the respective A–B and B–A–B block copolymers. Site transformation from the oxonium to the immonium active species is the key step in the polymerization mechanism. Finally, mechanistic aspects of the ring-opening polymerization of cyclic ester-amides are presented.

Di- and triblock copolymers with tetramethyleneoxy and trimethylene urethane repeating units were prepared by sequential polymerization of tetrahydrofuran (THF) and trimethylene urethane (TU) with the monofunctional initiator methyl trifluoromethanesulfonate (TfOMe) and the bifunctional initiator trifluoromethanesulfonic acid anhydride (TfOTf), respectively. The block copolymers obtained after purification show a uniform A-B resp. A-B-A microstructure as was deduced from NMR and GPC analyses. The block copolymers are semicrystalline materials with distinct melting points of the poly(THF) and the poly(TU) domains.

Chemical vapour deposition polymerisation of substituted [2.2]paracyclophanes is applied to the functionalised coating of stainless steel surfaces. Poly[o-trifluoroacetyl-p-xylylene-co-p-xylylene] (2a), poly[o-hydroxymethyl-p-xylylene-co-p-xylylene] (2b), poly[o-amino-p-xylylene-co-p-xylylene] (2c) and poly(p-xylylene-2,3-dicarboxylic anhydride) (2d) were deposited as thin layers.

Copolymerization of tetramethylene urea (TeU, 1) with the cyclic carbonates 2,2-dimethyltrimethylene carbonate (DTC, 2) and ethylene carbonate (EC, 3) results in the polyurethanes 4 and 5 with an approximate number-average molecular weight of 20 000 and a polydispersity index of two. Polyurethane 4 is an amorphous material with a glass transition temperature of 26.3°C; polyurethane 5 is a semicrystalline material with a melting temperature of 208°C. Distinct copolymerization mechanisms are proposed for the formation of polyurethane 4 and 5, respectively.

The cationic ring-opening polymerization of trimethylene urethane (tetrahydro-2 H-1,3-oxazin-2-one) in the melt with methyl trifluoromethanesulfonate as initiator results in poly(trimethylene urethane) in yields of ≈70%. Under the same reaction conditions 2,2-dimethyltrimethylene urethane (5,5-dimethyltetrahydro-2H-1,3-oxazin-2-one) cannot be polymerized. Poly(2,2-dimethyltrimethylene urethane), however, was obtained via polycondensation polymerization. Both polymers exhibit a uniform microstructure as deduced from NMR spectroscopic analysis. Ring-closing depolymerization in the melt with dibutyltin dimethoxide or titanium tetraisopropoxide at 140°C results the respective monomers in yields of ≈90%.

We report the first successful block copolymerization of ethylene and methyl methacrylate using a zirconocene-based catalyst system. The catalyst is generated in situ from Me2C(Cp)(Ind)ZrMe2 and B(C6F5)3 in toluene. Block copolymerization is achieved via the sequential addition of the monomers, starting with ethylene. The composition of the block copolymer is shown to be dependent on the time allowed for ethylene polymerization. The solubility of the resulting polymers, NMR data and GPC measurements are discussed, and a polymerization mechanism is proposed.