Polyamides based on a partially bio-based spirodiamine

In this study novel, fully and partially bio-based polyamides containing spiroacetal moieties in the backbone derived from bio-glycerol and bio-ethanol were prepared and characterized. The renewable diamine employed to obtain a series of polyamides was synthesized by means of thiolene click chemistry and therefore contains flexible thioether as well as rigid spiroacetal moieties. Two different chemical pathways for the polymerization were investigated and evaluated. The polymerization of polyamide salts proved to be the most promising method and therefore salt polymerization was applied in the synthesis of polyamides with aliphatic and aromatic di-carboxylic acids. Subsequently, the structure of the polymers was confirmed by Maldi-ToF analysis and additionally thermal and mechanical properties were investigated revealing T-g's between 24 and 80 degrees C and ductile materials with moduli between 1.0 and 1.5 GPa. Both semicrystalline and amorphous polyamides were thermally stable and therefore suitable for thermal processing. In the end, degradation studies were performed on the acetal containing polyamides which showed that the polymers were stable at pH 3 and higher

Thermoplastic polyacetals : chemistry from the past for a sustainable future?

Synthetic thermoplastic polyacetals have a long history dating back to 1912. While polymers with non-cyclic acetal repeat units are typically well soluble and degrade easily at biologically relevant pH values, polycycloacetals have a rigid polymer backbone, resulting in favorable thermal and mechanical properties but are often insoluble and thus challenging to process. In recent years, the degradation behavior and the availability of many building blocks from renewable resources have sparked renewed interest in poly(cyclo)acetals. This review provides a critical overview over the synthetic routes to polyacetals, highlighting where possible the material properties. Direct polyacetalization and polytransacetalization techniques are discussed first, followed by the polymerization of acetal containing monomers and recent ring opening polymerization approaches. Thermoplastic polyacetals show promise in delivery applications but also as bulk materials, where a combination of excellent material properties, a potential for renewable sourcing and degradation as an end-of-life option are of ever increasing importance

MacroRAFT agents from renewable resources and their use as polymeric scaffolds in a grafting from approach

Amphiphilic graft copolymers, based on renewable resources, were synthesized via a "grafting from" strategy. First, a linear hydroxyl functionalized aliphatic polyester, the monomer of which was a fatty acid derivative, was synthesized by a stepwise polymerization. Secondly, trithiocarbonate side groups were attached to the prepared polymer. Finally, a grafting from reversible addition-fragmentation chain transfer (RAFT) polymerization was executed on the macroRAFT agent with the aim to introduce poly(acrylic acid) grafts. The polymers prepared thereof were characterized by nuclear magnetic resonance spectroscopy, size exclusion chromatography and Fourier transform infrared spectroscopy. In order to show the amphiphilic character of those graft copolymers, micelle formation tests were carried out and measured with dynamic light scattering while emulsifying properties were studied via an emulsion stabilization test

Lignin inspired phenolic polyethers synthesized via ADMET : systematic structure-property investigation

A library of alpha,omega-dienes has been prepared via Williamson ether synthesis from aromatic diols, which can be extracted from lignin as biosource or exhibit related structural motifs. These dienes were subsequently subjected to acyclic diene metathesis polymerisation (ADMET). The molecular characterisation of monomers and polymers was performed using NMR spectroscopy, GC-MS, and SEC. The influence of the monomer structure on the thermal properties of the phenolic polyether polymers was investigated by DSC. Glass transition temperatures (T-g) in the range of -44 to 18 degrees C were detected depending on the monomer structure while TGA analysis showed degradation temperatures between 160 degrees C and 300 degrees C. T-g-values could be further increased up to a value of 110 degrees C by fast and versatile post-modification with 1,2,4-triazolinedione (TAD) click chemistry. In addition, the characteristic double bonds of the ADMET-derived polymer chains allowed for crosslinking by this TAD chemistry

Conformational influence of fluorinated building blocks on the physical properties of polyesters

The interplay of the relative configuration of diastereomeric vicinal difluoride groups on the conformational properties of polyesters has been investigated and compared to their non-fluorinated and per-fluorinated counterparts. The incorporation of syn and meso vicinal difluoride units in the polymer backbone was expected to influence the rigidity and stacking behaviour of the polymers in a significant way, and therefore to result in different thermal properties, such as melting point and melting enthalpy. Both syn and meso-2,3-difluoro butanediol have been reacted with the diester dimethyl succinate, leading to the formation of polyesters that have been characterized with H-1, C-13 and F-19 NMR. The polyesters showed molar masses up to 20 kg/mol (SEC). Surprisingly, the syn and meso-polymers displayed identical crystallization and melting behaviour. In contrast, differences were observed in the crystallization kinetics and melting points of syn and meso oligomers. Relying on time-resolved synchrotron SAXS and WAXD experiments, the complex multiple melting behaviour of these oligomers was explained in terms of crystal size and surface effects. The slower crystallization kinetics for the meso oligomers was tentatively associated with a stronger tendency to adopt gauche configurations. Apparently, such effects no longer affect the crystallization kinetics when larger polymers crystallize. It was also found that the syn and meso-polymers have identical equilibrium melting points and melting enthalpies notwithstanding molecular and crystallographic differences