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This work aims to produce poly(ethylene terephthalate)/multilayer graphene oxide (mGO) nanocomposites via continuous melt mixing in twin‐screw extrusion, and to study the changes in crystallization and melt flow behavior. Three mGO contents (0.05, 0.1, and 0.3 wt%) were used. Differential scanning calorimetry analyses showed that at 0.1 wt%, mGO acted best as nucleating agent, increasing the crystallization kinetics as well as the melt crystallization temperature (Tmc) by more than 20%. It was also observed that mGO increases the crystals perfection. The nucleating behavior was confirmed by X‐ray diffraction and small angle X‐ray scattering analyses, which showed a decrease in the composites' crystalline lamella thickness (lc) and long period. X‐ray microtomography data confirms that this behavior is significantly affected by the mGO agglomerates distribution and specific surface area inside the polymer matrix. The rheological behavior was studied under two different conditions. It was noticed that under lower shear stresses the mGO particles hinder the polymer flow, increasing the composites viscosity and the pseudo‐solid character. However, under higher shear stresses, for example, when flowing through a die, the nanomaterial enters its "superlubricity state," acting as a lubricant to the flow. This is industrially interesting, because it may allow the use of less severe processing parameters to produce the nanocomposites. [ABSTRACT FROM AUTHOR]

We report the synthesis and the crystal structure of isotactic poly((R,S)-3-methyl-1-pentene) (iP(R,S)3MP). A purely random achiral copolymer of two enantiomeric (R) and (S) 3-methyl-1-pentene monomers cannot be obtained by polymerization of the racemic mixture of the (R) and (S) monomers but has been obtained by stereospecific polymerization of 3-methyl-1,3-pentadiene to isotactic 1,2-poly(3-methyl-1,3-pentadiene) (iP3MPD12) and successive hydrogenation. The crystal structures of achiral iP(R,S)3MP and chiral poly((S)-3-methyl-1-pentene) (iP(S)3MP) are different, indicating that crystal structures of polymers may be driven by different entropic effects related to chirality and type of crystal disorder. The conformational disorder of the chiral lateral groups prevails in chiral iP(S)3MP, inducing crystallization of chains of one helical chirality, whereas the entropic effect due to the statistical substitution of chains of different helical chirality in the sites of the lattice prevails in achiral iP(R,S)3MP. [ABSTRACT FROM AUTHOR]

The resolution of the crystal structure and the physical properties of isotactic 1,2-poly(E-3-methyl-1,3-pentadiene) (iPE3MPD) are presented. This new polymer is one of the very few examples of known crystalline isotactic 1,2-polydienes. It does not crystallize by cooling from the melt but crystallizes by aging the amorphous samples at room temperature for several days and successive annealing. The stretching of amorphous or low crystalline compression-molded samples gives oriented fibers of a highly disordered mesomorphic form. Well-oriented fibers of the ordered crystalline form of iPE3MPD have been prepared by stretching amorphous or low crystalline compression-molded samples and successive annealing at 60-70 °C under tension. The crystalline structure of iPE3MPD is characterized by macromolecules in 7/2 helical conformation packed in an orthorhombic unit cell with parameters a = 17.4 Å, b = 16.5 Å, c = 15.3 Å according to the space group P21 ab. iPE3MPD has shown interesting mechanical properties of high deformability with elastic behavior associated with the crystallization during deformation of the mesophase that melts upon relaxation. [ABSTRACT FROM AUTHOR]

A study of the mechanical behavior of isotactic 1,2-poly(E-3-methyl-1,3-pentadiene) (iP3MPD) and of the structural and morphological transformations that take place upon stretching is presented. Amorphous samples do not show viscous flow but show high ductility, strain hardening, and elastomeric behavior. An unusual double yielding appears in the stress-strain curves that may be correlated to occurrence of events typical of yielding at low deformation followed by stress-induced crystallization of a mesomorphic form at higher deformation (200-300%). The yielding stress and an endothermic hysteresis effect at the glass transition simultaneously increase upon aging of the amorphous glass due to a local densification or formation of local order in the amorphous glass upon physical aging. The elasticity is accompanied by the crystallization of the mesophase during deformation and its melting upon relaxation. During successive cycles of tensile deformation and elastic recovery the yielding peak is still observed during every stretching step. The elasticity of iP3MPD is an unusual case of a polymer that shows rubbery elastomeric properties below the glass-transition temperature. [ABSTRACT FROM AUTHOR]