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A series of aliphatic-aromatic copolyesters based on poly(butylene terephthalate) (PBT) and poly(lactic acid) (PLA) have been synthesized by means of a novel reactive blending procedure coupled with polycondensation in melt. The obtained copolymers were further compared with PBT and PLA homopolymers and PBT/PLA non-compatibilized physical blends in order to investigate the effect of transesterification reactions on the structural, morphological, thermal and mechanical performance. Properties of the obtained materials have been found strictly dependent on the preparation process and blend/copolymer composition. The PBT/PLA physical blends appeared as highly crystalline, phase separated systems that exhibit brittle behavior. On the other hand, the applied method of reactive blending enhanced interfacial adhesion and promoted the arrangement of PBT and PLA in blocks of different lengths. Although the PBT-b-PLA copolyesters were found to be miscible in amorphous phase, the phase separation that has arisen from PBT crystalline domains occurs. Along with an increase in PLA weight fraction in copolymers, the length of aromatic sequences decreased which in turn resulted in shifting the values of melting temperatures (Tm) toward lower ones and decreased the degree of crystallinity (xc). Moreover, PBT-b-PLA copolymer with 30 wt% of PLA units has been demonstrated as a promising thermoplastic shape memory polymer (SMP) with a switching temperature of 35 °C. [ABSTRACT FROM AUTHOR]

Poly(trimethylene 2,5-furanoate) (PTF) nanocomposites reinforced with few layer graphene (FLG) were prepared through in situ polymerization. The method in question allows obtaining well-dispersed nanoplatelets in the whole volume of PTF matrix. The mechanical properties of the PTF/FLG nanocomposites slightly increased with as quantity of FLG as small as 0.1 wt%, which was best seen in the improvement of elongation at break by about two times. The presence of FLG did not affect the crystallization and chain mobility of PTF matrix. However, the incorporation of a small quantity of FLG slightly improved the thermal stability of the nanocomposites. Additionally, the cold and hot water absorption and oxygen permittivity measurements confirmed that FLG affected the tortuosity of the diffusive path for the penetrant molecule. Moreover, along with a successive addition of FLG a linear increase in thermal conductivity was visible. [ABSTRACT FROM AUTHOR]

Graphene nanoplatelets/single walled carbon nanotubes/poly(trimethylene terephthalate-block-poly(tetramethylene oxide) segmented copolymer (GNP/SWCNT/PTT-PTMO) hybrid nanocomposites were synthesized via in situ polymerization. A remarkable synergistic effect between GNPs and SWCNTs on improving thermal and mechanical properties of nanocomposites based on segmented block copolymers was observed. Heterogeneous structure of the PTT-PTMO allowed for a better and more uniform distribution of both types of nanoparticles and stabilized the structure in question. This enabled us to observe a so-called 'synergistic effect', caused by the use of mixture of carbon nanotubes and graphene nanopletelets, on the enhancement of thermal and mechanical properties of the obtained polymer. In order to ascertain the influence of mentioned carbon nanostructures on the nano-phase-separated structure of the synthesized PTT-PTMO block copolymers, differential scanning calorimetric (DSC) and dynamic mechanical thermoanalysis (DMTA) measurements were performed. Scanning electron microscopic (SEM) and transmission electron microscopic (TEM) images of the PTTPTMO nanocomposites displayed that hybrid nanofillers exhibited better distribution and compatibility than SWCNTs and GNPs did individually. The tensile modulus of 0.5SWCNT/0.1GNP/PTT-PTMO composites was 68% higher than that of the PTT-PTMO alone, compared to only a 10 and 28% increase in tensile modulus for 0.3GNP/PTT-PTMO and 0.3SWCNT/PTT-PTMO composites respectively (the highest concentration when single nanofiller was added). [ABSTRACT FROM AUTHOR]