Carbohydrate-based PBT copolyesters from a cyclic diol derived from naturally occurring tartaric acid: a comparative study regarding melt polycondensation and solid-state modification

2,3-O-Methylene-L-threitol (Thx) is a cyclic carbohydrate-based diol prepared by acetalization and subsequent reduction of the naturally occurring tartaric acid. The structure of Thx consists of a 1,3-dioxolane ring with two attached primary hydroxyl groups. Two series of partially bio-based poly(butylene terephthalate) (PBT) copolyesters were prepared using Thx as a comonomer by melt polycondensation (MP) and solid-state modification (SSM). Fully random copolyesters were obtained after MP using mixtures of Thx and 1,4-butanediol in combination with dimethyl terephthalate. Copolyesters with a unique block-like chemical microstructure were prepared by the incorporation of Thx into the amorphous phase of PBT by SSM. The partial replacement of the 1,4-butanediol units by Thx resulted in satisfactory thermal stabilities and gave rise to an increase of the Tg values, this effect was comparable for copolyesters prepared by MP and SSM. The partially bio-based materials prepared by SSM displayed higher melting points and easier crystallization from the melt, due to the presence of long PBT sequences in the backbone of the copolyester. The incorporation of Thx in the copolyester backbone enhanced the hydrolytic degradation of the materials with respect to the degradation of pure PBT.Peer ReviewedPostprint (published version

Aromatic thermotropic polyesters based on 2,5-furandicarboxylic acid and vanillic acid

This paper addresses a route to synthesize bio-based polymers with an aromatic backbone having a liquid crystalline (LC) phase in the molten state. The LC phase is employed to achieve uniaxial orientation during processing required in e.g. fiber spinning. For this purpose 2,5-furandicarboxylic acid (2,5-FDCA) and O-acetylvanillic acid (AVA), obtained from natural resources, are used as monomers. Similar to the 2,6-hydroxynapthoic acid used to perturb the crystalline packing of poly(oxybenzoate) in the Vectran® series, these bio-based monomers are used to lower the crystal to liquid crystal transition temperature. Considering that the poly(oxybenzoate) can also be obtained from natural resources, the adopted route provides the unique possibility to synthesize bio-based polymers that can be used for high performance applications. To obtain the desired polymers, a synthetic route is developed to overcome the thermal instability of the 2,5-FDCA monomer. Experimental techniques, such as optical microscopy, FTIR spectroscopy, DSC, and TGA are employed to follow the polymerization, phase transitions and evaluate thermal stability of the synthesized polymers

Chemistry, Functionality, and Coating Performance of Biobased Copolycarbonates from 1,4: 3,6-Dianhydrohexitols

Biobased polycarbonates were synthesized from 1,4:3,6-dianhydro-D-glucitol, 1,4:3,6-dianhydro-L-iditol, and 1,4:3,6-dianhydro-D-mannitol as the principal diols, using different types of carbonyl sources. The (co)polycarbonates resulting from polycondensation reactions in solution using triphosgene consisted of several types of polymer chains with respect to chain topology (e. g., linear or cyclic chains) and end-group structure (e. g., hydroxyl, chloroformate or alkyl chloride end-groups). The introduction of flexible comonomers seemed to increase the amount of cyclic structures in the product mixtures. The melt polymerization of diphenyl carbonate with 1,4:3,6-dianhydrohexitols required high reaction temperatures and led to almost exclusively hydroxy-functional poly(1,4:3,6-dianhydrohexitol carbonate)s. Copolymerizing the 1,4:3,6-dianhydrohexitols with 1,3-propanediol and diphenyl carbonate at high temperature resulted in the partial loss of 1,3-propanediol. On the other hand, by melt polycondensation of 1,4:3,6-dianhydrohexitol-based bis(phenyl carbonate) monomers in combination with primary diols and/or triols, the insertion of the primary alcohols could be achieved in a more controlled way. OH-functional materials were prepared, having suitable molecular weights, T(g) values, thermal stability, and melt viscosity profiles for (powder) coating applications. These functional biobased (co)polycarbonates were cured with polyisocyanate curing agents, resulting in colorless to pale yellow transparent, glossy coatings with good mechanical performance and solvent resistance. (C) 2011 Wiley Periodicals, Inc. J Appl Polym Sci 121: 1450-1463, 201

Partially renewable copolyesters prepared from acetalized d-glucitol by solid-state modification of poly(butylene terephthalate)

The backbone of poly(butylene terephthalate) (PBT) was modified with 2,4:3,5-di- O -methylene- D -glucitol (Glux) using solid-state modification (SSM). The obtained copolyest- ers proved to have a non-random overall chemical microstruc- ture. The thermal properties of these semicrystalline, block- like, Glux-based materials were extraordinary, showing higher melting points, and glass transition temperatures compared with other sugar-based copolyesters prepared by SSM. These remarkable thermal properties were a direct result of the inher- ently rigid structure of Glux and the relatively slow randomiza- tion of the block-like chemical microstructure of the Glux- based copolyesters in the melt. SSM proved to be a versatile tool for preparing partially biobased copolyesters with superior thermal propertiesPeer ReviewedPostprint (published version

Partially renewable copolyesters prepared from acetalized d-glucitol by solid-state modification of poly(butylene terephthalate)

The backbone of poly(butylene terephthalate) (PBT) was modified with 2,4:3,5-di- O -methylene- D -glucitol (Glux) using solid-state modification (SSM). The obtained copolyest- ers proved to have a non-random overall chemical microstruc- ture. The thermal properties of these semicrystalline, block- like, Glux-based materials were extraordinary, showing higher melting points, and glass transition temperatures compared with other sugar-based copolyesters prepared by SSM. These remarkable thermal properties were a direct result of the inher- ently rigid structure of Glux and the relatively slow randomiza- tion of the block-like chemical microstructure of the Glux- based copolyesters in the melt. SSM proved to be a versatile tool for preparing partially biobased copolyesters with superior thermal propertiesPeer Reviewe

Picosecond pulse control using semiconductor laser amplifiers

SIGLEAvailable from British Library Document Supply Centre- DSC:D61047 / BLDSC - British Library Document Supply CentreGBUnited Kingdo

Processing and performance of aromatic-aliphatic thermotropic polyesters based on vanillic acid

In this work we report on the processing, melt-drawing, and performance of new vanillic acid based aliphatic-aromatic thermotropic polyesters. It is demonstrated that these materials are easily processed from their nematic melts yielding highly oriented products. Furthermore, we demonstrate that a molecular weight (Mw) of roughly 30 kg/mol is required in order to successfully perform spinning on these polymers. The application of a polymer with lower Mw results in poor mechanical performance and fiber breakage during the winding process. Wide-angle X-ray diffraction analysis has been performed on the fibers and it is demonstrated that the orientation parameter increases with increasing draw-ratio of the fiber. Although these polymers are readily processed from their thermotropic melts, the obtained fibers only retain their orientation up to temperatures in the range of 120–130 °C, after which they start to melt. In general, these fibers exhibit tensile moduli in the range of ~10 GPa and a tensile strength around ~150 – 200 MPa. FTIR and solid-state NMR experiments indicate that only the aromatic components are molecularly oriented during the spinning process. In contrast, the aliphatic moieties exhibit a high mobility, normally corresponding to a local isotropic motion. It is expected that the poor molecular orientation of the aliphatic moieties in these aliphatic-aromatic thermotropic polyesters contribute to the relatively low tensile modulus of the fibers, obtained after the extrusion and melt-drawing process

Solid-state modification of PBT with cyclic acetalized galactitol and D-mannitol: Influence of composition and chemical microstructure on thermal properties

Two bicyclic carbohydrate-based diols, 2,3:4,5- di- O -methylene-galactitol (Galx) or 2,4:3,5-di- O -methylene- D - mannitol (Manx), were introduced into the backbone of poly(butylene terephthalate) using the solid-state modi fi cation technique (SSM). The resulting copolyesters had a unique block-like chemical microstructure that endows them with superior thermal properties when compared with their random counterparts obtained by melt copolymerization. The materials prepared by SSM displayed higher melting points, crystal- lization temperatures, and crystallinity due to the presence of long PBT sequences in the copolyester. The glass-transition temperatures also increased upon incorporation of the bicyclic comonomers, this e ff ect being more pronounced for Manx units. The melting points of these block-like copolyesters decreased after melting due to the occurrence of randomization, but they remained higher than those of copolyesters prepared from the melt. SSM was demonstrated to be a very suitable technique for the incorporation of rigid monomers into the amorphous phase of PBT, leading to bio-based non-random copolyesters with remarkable thermal propertiesPeer Reviewe