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Co- and terpolyesters based on succinic acid and isosorbide in combination with other renewable monomers such as 2,3-butanediol, 1,3-propanediol, and citric acid were synthesized and characterized. Linear polyesters were obtained via melt polycondensation of nonactivated dicarboxylic acids with OH functional monomers. Polymer end functionality (i.e., hydroxyl or carboxylic acid) was controlled by adjusting the monomer stoichiometry. The glass transition temperatures of the resulting polyesters could be effectively adjusted by varying the polymer composition and molar mass. By adding polyfunctional monomers such as trimethylolpropane or citric acid, polyesters with enhanced functionality were obtained. These biobased polyesters displayed functionalities and Tg values in the appropriate range for (powder) coating applications. The polyesters were cross-linked using conventional curing agents. Coatings from branched polyesters--hydroxyl as well as acid functional--showed significantly improved mechanical and chemical resistance compared to those formulated from linear polymers. These renewable polyesters proved to be suitable materials for coating applications with respect to solvent resistance, impact resistance, and hardness.

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Copolymerization of cyclohexene oxide (CHO) with alicyclic anhydrides applying chromium tetraphenylprophyrinato (TPPCrCl, 1) and salophen (SalophenCrCl, 2) catalysts resulted in polyesters or poly(ester-co-ether)s, depending on the nature of the catalyst, presence of a cocatalyst, solvent and type of anhydride. The combination of 1 as catalyst and 4-N,N-dimethylamino-pyridine (DMAP) as cocatalyst in the copolymerization of CHO with succinic anhydride (SA), cyclopropane-1,2-dicarboxylic acid anhydride (CPrA), cyclopentane-1,2-dicarboxylic acid anhydride (CPA) or phthalic anhydride (PA) invariably resulted in a completely alternating topology and therefore a pure polyester. Contrarily, 2 in combination with DMAP did not afford pure polyesters for the copolymerization of CHO with SA or CPrA but did render the alternating topology when CPA or PA was used as anhydride comonomer. Water proved to be an efficient bifunctional CTA affording α,ω-hydroxyl-terminated polyesters without loss of catalytic activity. When CO2 was introduced as additional monomer to CHO and the anhydrides, both 1 and 2 in combination with DMAP as cocatalyst afforded perfect poly(ester-co-carbonate)s. The presence of CO2 effectively prevents the undesirable side reaction of oxirane homopolymerization.

The catalytic behavior of several inexpensive and simple N-heterocyclic organic catalysts in ring-opening polymerization (ROP) of ω-pentadecalactone (PDL) and ε-caprolactone (CL) has been studied. The polymerization reactions, carried out in bulk monomer and in toluene solution at 100 °C, identified 1,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD) in combination with benzyl alcohol (BnOH) as initiator as the only active catalyst for the ring-opening polymerization of PDL and for the copolymerization of PDL and CL. The guanidine N-methyl-TBD (MTBD), 1,2,3-triisopropylguanidine, the amidine 1,8-diazabicycloundec-7-ene (DBU), and other N-heterocyclic organic catalysts such as dialkylaminopyridine (DMAP), imidazole, indoles, and N-heterocyclic carbenes (NHC's) tested in this study proved to be inactive in the ROP of PDL even for the long reaction times. The polymerization mechanism, kinetic studies, temperature, and monomer concentration effects were investigated both in solution and in bulk monomer. The pseudoliving character of the TBD/BnOH system has been proven by kinetic studies in both toluene solution and bulk monomer. By varying the experimental conditions and the monomer feed composition, highly crystalline poly(PDL-co-CL) random copolymers of various compositions have been prepared using the binary system TBD/ROH as catalyst/initiators. Thermal analysis and 13 C NMR spectroscopy show a linear relation of the variation of the random copolymers melting temperatures as a function of comonomer content.

The synthesis of [PhC(NSiMe3)2]2Y(μ-Cl)2Li·2THF (1) from YCl3·3.5THF and [PhC(NSiMe3)2]Li, which is easily transformed into [PhC(NSiMe3)2]2YCl·THF (2), provides a useful entry into the chemistry of several bis(N,N‘-bis(trimethylsilyl)benzamidinato)yttrium complexes. Those prepared from 2 by chloride metathesis include [PhC(NSiMe3)2]2YR (R = BH4·THF (3), N(SiMe3)2 (4), 2,6-(CMe3)2-4-MeOC6H2 (5), (μ-Me)2Li·TMEDA (6) (TMEDA = N,N,N‘,N‘-tetramethylethylenediamine), CH2Ph·THF (7), CH(SiMe3)2 (8)). Similar to 8, [p-MeOC6H4C(NSiMe3)2]2YCH(SiMe3)2 (8 OMe ) could be prepared starting from [p-MeOC6H4C(NSiMe3)2]2YCl·THF (2 OMe ). Hydrogenolysis (4 atm) of 8 and 8 OMe affords dimeric hydrides {[p-X-C6H4C(NSiMe3)2]2Y(μ-H)}2 (X = H (9), X = MeO (9 OMe )). The alkyl 8 OMe and the hydride 9 have been characterized by an X-ray diffraction structure determination. Sterically the bis(N,N‘-bis(trimethylsilyl)benzamidinate) ligand system resembles more the bis(pentamethylcyclopentadienyl) than the bis(cyclopentadienyl) ligand set. However, INDO/1 semi-empirical MO studies indicate that the electronic properties of [HC(NH)2]2YCH3 (used as a model for bis(benzamidinato)yttrium alkyl complexes) are rather different from [C5H5]2YCH3. The yttrium atom in [HC(NH)2]2YCH3 is considerably more positively charged than in [C5H5]2YCH3. The resulting strong ionic character of the bis(benzamidinate) system is held responsible for the absence of agostic interactions and H/D exchange and the low hydrogenolysis rate observed.

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The biomass-based monomer isosorbide was incorporated into poly(butylene terephthalate) (PBT) by solid-state polymerization (SSP) using the macrodiol monomer BTITB-(OH) 2, which consists of isosorbide (I), terephthalic acid (T), and 1,4-butandiol (B) residues. This macromonomer can be synthesized by a simple one-pot, two-step reaction. Polymers with number-average molecular weights up to 100,000 g x mol (-1) were readily synthesized from various ratios of PBT/BTITB-(OH) 2. Their molecular weights, thermal properties, and colors were compared with corresponding copolyesters that were obtained by melt polycondensation. We found that T m, T c, and especially T g were superior for materials that were obtained by SSP. This is ascribed to differences in the microstructures of both types of copolyesters; the SSP products exhibit a more blocky structure than do the more random melt-polymerized counterparts. The SSP method resulted in much higher molecular weights and much less colored polymers, and it seems to be the preferred route for incorporating biobased monomers that exhibit limited thermal stability into engineering plastics.