Kinetic analysis of the swelling behavior of poly(n-butylacrylate-1,6- hexanedioldiacrylate) networks in 4-cyano-4 0 -n-pentyl-biphenyl (5CB) Tewfik Bouchaour, 1,2 Zohra Bouberka, 1,3 Boum  edie`neDaliYoucef, 1,2 Ulrich Maschke 1 1 Unit e Mat eriaux et Transformations—UMET (UMR CNRS No. 8207), B^ atiment C6, Universit e Lille 1—Sciences et Technologies, Villeneuve d’Ascq Cedex 59655, France 2 Laboratoire de Recherche sur les Macromol ecules (LRM), Facult e des Sciences, Universit e Aboubakr Belka € ıd, Tlemcen 13000, Algeria 3 Laboratoire Physico-Chimie des Mat eriaux-Catalyse et Environnement (LPCM-CE), Universit e des Sciences et de la Technologie d’Oran, USTO, BP 1505, El M’naouer, Oran 31000, Algeria Correspondence to: U. Maschke (E - mail: ulrich.maschke@univ-lille1.fr) ABSTRACT: The dynamic swelling behavior of chemically crosslinked poly(n-butylacrylate/1,6-hexanedioldiacrylate) [poly(Abu-HDDA)] networks, immersed in an nematogenic and two isotropic solvents, was experimentally analyzed. These networks were elaborated by ultraviolet (UV)–visible light-induced radical polymerization/crosslinking reactions of Abu/HDDA mixtures, to yield poly(Abu/0.5 wt % HDDA) and poly(Abu/5 wt % HDDA) networks corresponding to weakly and strongly crosslinked systems, respectively. The swelling behavior of these poly(Abu-HDDA) networks was investigated by immersion in excess solvent, followed by subsequent measurements of the variation of the sample size by means of optical microscopy, depending on temperature and immersion time. Methanol and toluene were employed as isotropic solvents and the nematic liquid crystal molecule 4-cyano-4 0 -n-pentyl-biphenyl, was considered as anisotropic medium. Swelling ratios were calculated by taking into account diameter sizes as function of immersion time compared to the dry state. Experimental data were analyzed using the Komori–Sakamoto approach and the results of this model were found to be in good agree- ment with the obtained data. The plateau values of the swelling curves at equilibrium were used to establish phase diagrams as function of temperature and solvent concentration. V C 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 45452. KEYWORDS: crosslinking; liquid crystals; phase behavior; photo-polymerization; polymer networks; swelling Received 11 May 2017; accepted 23 June 2017 DOI: 10.1002/app.45452 INTRODUCTION Properties of swelling and deswelling of polymer networks in isotropic solvents attracted considerable attention over the past decades. 1–10 Flory and Rehner 11 reported on a theory of rubber elasticity based on a swelling equilibrium between the osmotic pressure of solvent supporting swelling and the elastic forces of the crosslinking points being opposed to the extension of the mesh sizes of the networks. The dynamics of gel swelling and deswelling was investigated in detail by Tanaka et al. 12–14 who established a theoretical formal- ism characterizing the dynamics of the gel. This procedure and the extensions of this approach 15–27 were largely applied to describe experimental results from immersed polymer gels. In 1977, Tanaka et al. 28 noticed that polyacrylamide networks swo- len in water/acetone can experience immense volume changes by varying the concentration of the two solvents. 29,30 Such large volume variations were found under particular circumstances, for example, for immersion of crosslinked polymer networks in specific solvents, and has guided to various studies leading to a great choice of practical applications. Responsive polymer gels and their swelling behavior remain along the topics which maintain a special attention nowadays. 4,5,31–43 Upon small stimuli-like modification of pH, temperature, pres- sure, or application of shearing force, electric or magnetic fields, these systems can experience swelling or deswelling effects. Efforts were also dedicated to develop artificial muscles on the basis of main chain and side chain liquid crystalline (LC) poly- mers. 34,44–51 In a narrow temperature range, main chain nematic polymer networks greatly improve the ability to be used as artifi- cial muscles over nematic side chain elastomers. Investigation of swelling and deswelling kinetics represents a key factor for appli- cation purposes of polymer gels as mechanical actuators. Following these lines, research interests were focused on the swelling behavior of mainly photochemically crosslinked polymer networks V C 2017 Wiley Periodicals, Inc. WWW.MATERIALSVIEWS.COM J. APPL. POLYM. SCI. 2017, DOI: 10.1002/APP.45452 45452 (1 of 8)