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Adding nanofillers Cloisite 30B (C30B) and Cloisite 15A (C15A) to poly(ethylene terephthalate) (PET)/poly(ε‐caprolactone) (PCL) (70/30, wt/wt) blends via melt blending can improve their phase morphology and change their interface properties. The effects of the different selective localization of clay on the structure and the morphologies are studied and evaluated by theoretical and experimental methods. It is found that C30B is selectively localized in PET and at the PET‐PCL interface, whereas C15A is mainly localized at the interface. Moreover, the changes in the rheological behavior of the blends are attributed to the formation of clay network‐like structures. X‐ray diffraction, scanning electron microscope, and transmission electron micrograph observations also evidenced an exfoliated and/or intercalated structure of C30B, and intercalated structure of C15A in the blend, together with significant morphology changes of the initially immiscible blend. The relative permeability to PET/PCL of the nanocomposites decreased with the increasing of nanoclays content. © 2020 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020, 137, 48812. [ABSTRACT FROM AUTHOR]

Abstract: In this work, the synthesis and characterization of triple‐shape and two‐way shape‐memory effect of novel poly(ester‐urethane)s (PURs) made of a poly(ε‐caprolactone) (PCL) and poly(ω‐pentadecalactone) (PPDL) segments and N,N‐bis(2‐hydroxyethyl)cinnamide (BHECA) monomer by reactive extrusion (REx) is reported. PCL and PPDL are chosen as semicrystalline segments because of their inherent ability to undergo tensile elongation upon cooling, as prerequisite for the two‐way shape‐memory effect. BHECA is used as the “cross‐linker” due to its ability to participate in reversible [2+2] cycloaddition reaction and to mainly maintain the crystalline features of semicrystalline precursors within these PURs. This novel simple strategy is considered extremely versatile and adaptive because of the possibility to vary crystallizable segments and coupling agents, thus paving the way to the design of a multitude of triple (or more) shape‐memory polymers with two‐way behavior. Feasibility with PURs containing PCL, PPDL, and BHECA is demonstrated by adjusting the shape‐memory behavior (one and two‐way effects), and studying the structure–property relationships of the resulting PURs by DSC, DMTA, and 2D wide angle X‐ray scattering analyses while varying the weight composition of the two semicrystalline segments. [ABSTRACT FROM AUTHOR]

Several copolyesters were synthesized from carboxytelechelic poly(-caprolactone) and bis(2-hydroxyethyl)terephthalate (BHET), using a two-step method and a one-step method providing regular and random distributions of starting comonomers in the copolyester chains, respectively. Even with an identical molar comonomer composition, the properties of obtained copolyesters depended on the synthesis method, therefore the comonomer distribution along the polymer chain. The copolyester structure was characterized by ¹H and 13C NMR and FTIR spectroscopy. The thermal properties of synthesized copolyesters were also studied by DSC and TGA demonstrating the influence of aromatic rings spread along the macromolecular polyester chain. [ABSTRACT FROM AUTHOR]

Abstract: The lamellar structure of montmorillonite (MMT) clays exhibits an interesting potential to improve the barrier properties of thermoplastic polyurethanes (TPU). However direct melt blending of an ester-based TPU and functional organoclays, despite showing good filler dispersion, did not allowed for improving neither barrier properties (i.e., sorption and diffusion to water vapor) not mechanical performances with respect to the unfilled TPU. Therefore, two alternative strategies involving poly(ε-caprolactone) (PCL)/organoclay masterbatches were explored to investigate the possibility to prepare materials with improved mechanical and barrier properties. In the first strategy, a PCL/organoclay masterbatch with high inorganic content was obtained by melt-blending (coined “free PCL” masterbatch), whereas in the second strategy PCL-grafted organoclay nanohybrids, also with high inorganic content were synthesized by in situ intercalative grafting/ring-opening polymerization of ε-caprolactone (CL). Purposely, ROP of CL was initiated from hydroxyl groups available onto the MMT surface actually organo-modified by alkylammonium cations bearing hydroxyl functions (coined “nanohybrid PCL” masterbatch). These highly-filled PCL masterbatches (with ca. 25wt% in inorganics) were then added into the ester-based TPU to prepare nanoclay/polyurethane nanocomposites by melt-blending. The morphology and dispersion of the resulting materials were characterized by X-ray diffraction and transmission electron microscopy. Improved sorption and diffusion properties towards water vapor as well as mechanical properties were measured. Herein, these results are discussed as a function of both clay dispersion and matrix/organoclay interaction. [Copyright &y& Elsevier]

Abstract: Poly(ε-caprolactone)-coated (covalently grafted and physisorbed) multi-walled carbon nanotubes (MWCNTs) were synthesized by ring-opening polymerization (ROP) of ε-caprolactone initiated from primary amines grafted on the MWCNT surface through the exposure to atomic nitrogen generated in a microwave-induced plasma. The morphology of the recovered nanohybrids and the amount of grafted polymer chains were studied by transmission electron microscopy (TEM) and thermogravimetric analysis (TGA), respectively. These nanohybrids were used as highly filled masterbatches to be dispersed within either poly(ε-caprolactone) (PCL) or high-density polyethylene (HDPE) matrices in the molten state. The thermal behavior as well as the electrical properties of the so-produced nanocomposites were characterized and correlated to their morphology. The HDPE filled with PCL-coated MWCNTs nanohybrids showed better electrical properties than HDPE filled with non-modified MWCNTs. The electrical properties improvement was associated to a better dispersion of the PCL-coated MWCNTs and, also, to the exclusive presence of PCL coating in tunneling junction between the nanotubes. [Copyright &y& Elsevier]

Abstract: Poly(epsilon-caprolactone) (PCL) nanocomposites containing carbon nanotubes, layered silicates, sepiolite or polyhedral oligomeric silsesquioxane (POSS) were characterized by advanced thermal analysis. Adding carbon nanotubes or layered silicates increases the excess heat capacity in quasi-isothermal crystallization experiments by MTDSC, pointing to an increased fraction of reversibly melting and crystallizing material. In situ AFM during isothermal crystallization and SAXS during subsequent heating reveal an altered PCL semi-crystalline morphology. The nucleating ability of the carbon nanotubes induces a striking transcrystalline morphology, promoting the growth of secondary PCL crystals with an increased fold surface energy and a reduced melting temperature. The altered crystalline-amorphous interphase at the crystal fold surface houses the material that reversibly crystallizes and melts under quasi-isothermal crystallization conditions. A fraction of this interphase is not able to crystallize but converts into glassy, rigid amorphous material upon cooling prior to reaching the PCL main glass transition temperature. Low aspect ratio sepiolite and POSS nanofillers barely nucleate the PCL crystallization and therefore hardly affect the PCL semi-crystalline morphology and thermal behavior. [Copyright &y& Elsevier]

Abstract: In this work, the nucleation and crystallization behavior of melt mixed PCL/CNT nanocomposites has been studied. The mixtures of PCL and pristine MWNTs were prepared by extrusion with different nanofiller contents: 0.3, 0.5, 0.7, 1 and 3%. Standard DSC measurements demonstrated pronounced nucleation effects as well as increases in PCL crystallinity. The nucleation effect saturates at only 0.5% (a value much lower than those previously reported in the literature for similar nanocomposites) indicating that the dispersions obtained were excellent. This was corroborated by both TEM observations and by the determination of a very low dielectric percolation threshold (i.e., 0.3%). In self-nucleation experiments, supernucleation effects were obtained up to a maximum of approximately 200% efficiency. This is the first time that supernucleation effects of this order have been reported for PCL filled with untreated MWNTs, a result that we attribute to the excellent dispersion achieved. Isothermal crystallization experiments performed by DSC showed an increase in the crystallization kinetics of PCL with increases in MWNT content as a consequence of the supernucleation effect. The Avrami equation successfully described the overall crystallization kinetics and while neat PCL exhibited Avrami indexes close to 3, indicating that instantaneously nucleated spherulites were formed, the nanocomposite yielded mostly Avrami index values close to 2, as expected for axialites instantaneously nucleated on the surface of the MWNTs. Remarkably, the temperature dependence of the overall crystallization rate exhibited a dramatic change with MWNT content. This novel effect was described as a crystallization regime change (i.e., from Regime II to Regime III) induced by the presence of the MWNTs in terms of the Lauritzen and Hoffman theory. [Copyright &y& Elsevier]