Modified polyacrylonitrile blends with cellulose acetate: blend properties Byung Kyu Kim a, * , Young Se Oh b , Young Min Lee a , Lee Keun Yoon a , Soo Lee c a Department of Polymer Science and Engineering, Pusan National University, Pusan 609-735, South Korea b Research and Development Center, Hanil Synthetic Fiber Company Ltd., Masan 630-791, South Korea c Department of Chemistry, Changwon National University, Changwon 641-773, South Korea Received 17 September 1998; received in revised form 8 February 1999; accepted 11 February 1999 Abstract Polyacrylonitrile (PAN) was modified by copolymerizing with methyl acrylate (MA) and 2-acrylamido-2-methyl propane sulfonic acid (AMPS abbreviated as AP), and blended with cellulose acetate (CA) in dimethyl formamide. Scanning electron microscopy (SEM) showed much finer domain morphology for MA–PAN blends than AP–PAN blends. Dynamic mechanical property measurements showed an inward migration of the two glass transition temperatures (T g ) viz., T g ’s of PAN and CA, however the migration of PAN T g was more pronounced in AP–PAN blends, the result agreed well with the conjugate phase calculation. The phase inversion composition, calculated using Coran–Patel model agreed well with SEM morphology.  1999 Elsevier Science Ltd. All rights reserved. Keywords: Polyacrylonitrile; Cellulose acetate; Coran–Patel model 1. Introduction Blending may be used effectively to modify the properties of polymer materials. This method is based on the theore- tical possibility of controlling the properties of polymers by modifying their chemical compositions and molecular struc- tures by means of the appropriate selection of miscible poly- mers [1–3]. Miscible polymer blends are really new materials with completely different properties, and fabri- cated articles may possess good mechanical properties. However, well established miscible polymer blends are very rare. Immiscible polymer blends generally have a coarse morphology which is reflected in their poor mechan- ical properties. If on the other hand it is possible to obtain a highly dispersed mixture from immiscible polymers, fabri- cated articles may combine the properties of the component polymers. Polyacrylonitrile (PAN) and cellulose acetate (CA) have been the subject of current researches, because both poly- mers can easily produce fibers in a common organic solvent, e.g. N,N-dimethyl formamide (DMF). It has been reported [4–6] that PAN–CA blend is immiscible. However, if CA– PAN graft copolymer is added to this blend, considerable improvements in the homogeneity and the stability of the solution blends are obtained. Unfortunately, this system has not yet been industrialized due to the poor economic benefit of processing. It has been known that PAN is rarely compatible with most other polymers due to the strong dipole–dipole inter- actions of nitrile groups [7,8]. However, CA is compatible with several synthetic polymers having electron-rich pendant group, such as poly(4-vinyl pyridine) [9,10]. Fiber-forming PAN has been generally modified with a small amount of amorphous vinyl monomers to give better processability and dyeability [11,12]. As a continuation of our earlier efforts to modify the properties of PAN [13–15], in this experiment we prepared two types of PAN copolymers with methyl acrylate (MA) and 2-acrylamido-2-methylpropane sulfonic acid (AMPS), and the miscibilities of these PAN copolymers with CA have been studied in terms of morphology, dynamic mechanical, and mechanical properties of the blends. 2. Experimental 2.1. Materials and preparation of samples Cellulose acetate (CA) was purchased from Aldrich. The degree of polymerization and degree of substitution were 160 and 2.4, respectively. Copolymers containing 8 wt% of MA (hereafter called MA–PAN) and AMPS (hereafter called AP–PAN) were prepared as follows. Copolymeriza- tion was carried out in 50 wt% DMF at 70°C for 10 h under Polymer 41 (2000) 385–390 0032-3861/00/$ - see front matter  1999 Elsevier Science Ltd. All rights reserved. PII: S0032-3861(99)00148-2 * Corresponding author. Tel.: +82-51-510-2406; fax: +82-51-514-1726. E-mail address: bkkim@hyowon.pusan.ac.kr (B.K. Kim)