Materials Science and Engineering A 521–522 (2009) 259–262 Contents lists available at ScienceDirect Materials Science and Engineering A journal homepage: www.elsevier.com/locate/msea Morphology and dynamical behaviour of grafted copolymers S. Etienne a,b,∗ , J.M. Hiver a , M. Billy c , A. Jonquières c , R. Clément c , I. Stevenson d , E. Nikaj d , L. David d a Laboratoire de Physique des Matériaux, UMR CNRS 7556, Ecole Nationale Supérieure des Mines, Nancy Université, Parc de Saurupt, 54042 Nancy, France b EEIGM, Nancy Université, 6 rue Bastien Lepage, 54010 Nancy, France c Laboratoire de Chimie Physique Macromoléculaire, UMR CNRS 7568, Ecole Nationale Supérieure des Industries Chimiques, 1 rue Grandville, BP20451, 54001 Nancy Cedex, France d Laboratoire des Matériaux Polymères et des Biomatériaux, Université de Lyon, Université Lyon 1, UMR 5223 IMP, Bât. ISTIL, 15, bd Latarjet, 69622 Villeurbanne Cedex, France article info Article history: Received 17 June 2008 Accepted 22 September 2008 Keywords: Cellulose acetate Grafted copolymers Mechanical spectroscopy Dielectric spectroscopy Physical aging abstract The interactions between the main chain and lateral chains in grafted polymers play an important role on their dynamics. This is a complex issue, since several length scales are to be taken into account, from the local intramacromolecular interactions between linked moieties up to intermolecular interactions in phase separated systems. Such phenomena are investigated on the basis of new copolymers obtained by controlled radical polymerization. The effect of two parameters are studied separately, namely (i) the number of grafted chains on the main chain (cellulose acetate) and (ii) the length of grafted moieties (poly(methyl(diethylene glycol)methacrylate)). The dynamics of molecular motions was assessed by Low Frequency Mechanical Spectroscopy and Broad Band Dielectric Spectroscopy. The complex shear and dielectric moduli were measured on thin films (60 m thickness) as a function of frequency and temperature. The sensitivity of these relaxation spectroscopy techniques, as compared to calorimetry measurements, allowed to study the effects of (i) the chemical structure of the copolymers and (ii) the microstructure at the nanoscale, as investigated by Small Angle X-ray Scattering. It is shown that the main parameter is the soft grafted moities content: as expected the molecular mobil- ity increases as the content of soft grafted chains increases. In addition, it is shown that this molecular mobility is drastically depressed by thermal treatment. © 2009 Elsevier B.V. All rights reserved. 1. Introduction Ethyl-tert-butyl ether (ETBE) is both (i) an environment-friendly fuel octane enhancer and (ii) one of the most promising biofu- els. Purification of ETBE is a current challenge. In the industrial synthesis process of ETBE, an azeotropic mixture (ethanol/ETBE) is obtained. The conventional separation process is a ternary distillation. An economical alternative from the energy point of view is a hybrid process involving a membrane separation mod- ule. The main characteristics of a membrane are the selectivity C ′ and the pervaporation flux J. Cellulose acetate (CA) exhibits a very high selectivity but the flux is low. In order to increase the flux, degrees of freedom have to be introduced in CA. This goal can be achieved by grafting CA macromolecules with soft (i.e. low T g ) chains. Poly(methyl(diethylene glycol)methacrylate) (MDGMA) is chosen for this purpose. Increasing the molecular mobility of CA ∗ Corresponding author at: Laboratoire de Physique des Matériaux, UMR CNRS 7556, Ecole Nationale Supérieure des Mines, Nancy Université, Parc de Saurupt, 54042 Nancy, France. Tel.: +33 3 83 36 83 14. E-mail address: Serge.Etienne@eeigm.inpl-nancy.fr (S. Etienne). increases the permeability, as expected, but as a result selectivity is decreased [1]. Thus, a compromise is to be found. Two param- eters are studied, namely the number and the length of grafted chains. In order to explain these results at the molecular scale, the morphology was studied by means of X-ray scattering (small and wide angles), the molecular dynamics were assessed by means of mechanical and dielectric spectroscopy. Finally the characteristic temperatures were determined by calorimetric analysis. Actually, intensive research work has already been devoted to physical aging and relaxation processes in CA and CA-based blends [2–7]. The aim of this work is to study the grafted CA with a particular attention paid to thermal treatments and molecular architecture. 2. Materials The effect of two parameters are studied separately, namely (i) the number of grafted chains on the main chain and (ii) the length of grafted moieties. This is achieved in the case of cel- lulose acetate (purchased from Fluka, M n = 52000 g/mol, 40 wt.% acetyl) grafted with poly(methyl(diethylene glycol)methacrylate) (so called poly(MDEGEMA)) synthesized by Atom Transfer Radi- cal Polymerization (ATRP). The grafted moieties were either long 0921-5093/$ – see front matter © 2009 Elsevier B.V. All rights reserved. doi:10.1016/j.msea.2008.09.104