Eur. Phys. J. Special Topics 189, 273–277 (2010) c  EDP Sciences, Springer-Verlag 2010 DOI: 10.1140/epjst/e2010-01332-x T HE EUROPEAN P HYSICAL JOURNAL SPECIAL TOPICS Regular Article Eﬀect of guest-host interaction on the dynamics of ethylene glycol in H-ZSM5 zeolite V.K. Sharma 1 , S. Mitra 1, a , P. Maheshwari 2 , D. Dutta 2 , and P.K. Pujari 2 , and R. Mukhopadhyay 1 1 Solid State Physics Division, Bhabha Atomic Research Centre, Mumbai 400 085, India 2 Radiochemistry Division, Bhabha Atomic Research Centre, Mumbai 400 085, India Received 01 September 2010 / Received in ﬁnal form 14 September 2010 Published online 12 November 2010 Abstract. Dynamics of ethylene glycol (EG) adsorbed in H-ZSM5 zeo- lite as studied using quasielastic neutron scattering (QENS) technique is reported here. Analysis of QENS data revealed that observed dy- namics correspond to isotropic rotational motion of EG. Rotational diﬀusion coeﬃcient of EG adsorbed in H-ZSM5 zeolite is found to be slower compared to bulk and comparable to that of benzene adsorbed in the same host. Positron Annihilation Spectroscopy (PAS) technique is used to understand the nature of guest-host interaction and the results of both QENS and PAS are found to be consistent with each other. 1 Introduction There have been reports in the literature on the eﬀect of conﬁnement on several properties of ﬂuids like structure, diﬀusivity, freezing behaviour, etc. [1]. Diﬀusion of liquid in restricted geometries is determined by a combination of two factors: geomet- rical constraint and guest-host interaction. The modiﬁcation in dynamics of liquids in conﬁned geometry compared to its bulk state has attracted considerable interest in scientiﬁc research, not only for fundamental aspects but also for practical applications in many pertinent industrial problems, in petroleum industries, catalysis, water puriﬁ- cation, building optical switches and so forth. Zeolites oﬀer a conﬁned system which is used in wide range of cation exchange, catalytic and molecular sieving properties etc., elucidation of which requires an understanding of diﬀusivity of the adsorbed molecules [2]. Diﬀusivity of guest molecules depend on many factors such as size and shape of the guest molecule, temperature, concentration, guest-host interactions etc [3–5]. Diﬀusion of several hydrocarbons (acetylene, propylene, butadiene etc.) in diﬀerent zeolites (e.g. ZSM5, Na-Y etc.) had been studied by us using quasi-elastic neutron scattering technique (QENS) and molecular dynamics (MD) simulation tech- niques [6–10]. QENS technique is used to study motions occurring at time scales in the range 10 -9 –10 -13 s and covering length scale in the range of angstrom ( ˚ A) [11]. EG(HO-CH 2 -CH 2 -OH) can form hydrogen bond with the oxygen of host zeolite and it will be interesting to study the eﬀect of guest-host interaction on its dynamical a e-mail: smitra@barc.gov.in