Macromolecular Nanotechnology Comparison of thermal and dielectric spectroscopy for nanocomposites based on polypropylene and Layered Double Hydroxide – Proof of interfaces Purv J. Purohit a,1 , De-Yi Wang b,c , Andreas Wurm d , Christoph Schick d , Andreas Schönhals a,⇑ a BAM Federal Institute for Materials Research and Testing, Unter den Eichen 87, 12205 Berlin, Germany b IMDEA Materials, Parque Científico de la Universidad Carlos III de Madrid, Avda. del Mediterráneo, N°22, 28918 Leganés, Spain c Centre for Degradable and Flame-Retardant Polymeric Materials (ERCEPM-MoE), College of Chemistry, Sichuan University, Chengdu 610064, China d Universität Rostock, Institute of Physics, Wismarsche Strasse 43-45, 18051 Rostock, Germany article info Article history: Received 2 October 2013 Received in revised form 24 February 2014 Accepted 3 March 2014 Available online 22 March 2014 Keywords: Polypropylene Layered Double Hydroxide Nanocomposites Temperature Modulated Differential Scanning Calorimetery Dielectric spectroscopy Rigid amorphous fraction abstract Polymer based nanocomposites by melt blending of synthesized ZnAl-Layered Double Hydroxide (ZnAl-LDH) and polypropylene (PP) were investigated by temperature modu- lated differential scanning calorimetry (TMDSC). The LDH was organically modified by using a surfactant, sodium dodecylbenzene sulfonate (SDBS) to increase the interlayer spacing of the LDH, so that polymer segments can intercalate the inter layer galleries. The glass transition temperature (T g ) and the thermal relaxation strength (Dc p ) were deter- mined. The T g remains constant for concentration till 12 wt% of LDH and a slight reduction of 3 K might be observed for 16 wt% LDH but within the experimental error. The thermal relaxation strength decreases indicating reduction in the amount of mobile polymer seg- ments from amorphous fraction. This finding is supported by the increase in the rigid amorphous fraction (RAF) which is attributed to the polymer molecules which are in close proximity to the crystals and the LDH sheets, as they hinder their mobility. This is analyzed in detail and related to the dielectric relaxation spectroscopy (BDS) results. Ó 2014 Elsevier Ltd. All rights reserved. 1. Introduction Modification of polymeric materials employing nano- sized fillers to improve material characteristics such as gas and solvent barrier, toughness, mechanical strength and flame retardancy is explored by scientists and researchers worldwide [1–7]. An increasing number of review articles are published on structure–property relationships of polymer nanocomposites. (For instance see the Ref. [8–11]). The expected property enhancement obtained for this new class of materials is related to the small size of the filler material and its homogeneous dis- persion on a nanometer scale. Therefore, the length scale of interaction of the nano-fillers with the matrix corre- sponds to several polymer segments. Due to the small size of the particles they have also a high surface to volume ra- tio which results in a high volume fraction of an interfacial area between the polymer matrix and the nanoparticle [12]. The structure of the polymer chains in these interfa- cial regions, like the crystallinity, the packing density, and/or the molecular mobility of the segments in that interface can be different from those in the matrix polymer [13–16]. With regard to the latter point a change in the molecular mobility of the segments means that the glass transition in these interfacial regions might be different http://dx.doi.org/10.1016/j.eurpolymj.2014.03.005 0014-3057/Ó 2014 Elsevier Ltd. All rights reserved. ⇑ Corresponding author. Tel.: +49 30 8104 3384; fax: +49 30 8104 1617. E-mail address: andreas.schoenhals@bam.de (A. Schönhals). 1 Present address: Clear Edge Filtration, Kevelaerer Straße 78, 47608 Geldern-Walbeck, Germany. European Polymer Journal 55 (2014) 48–56 Contents lists available at ScienceDirect European Polymer Journal journal homepage: www.elsevier.com/locate/europolj MACROMOLECULAR NANOTECHNOLOGY