Macromolecules zyxwvu 1992,25, zyxwvu 63614364 6361 Noncrystalline Order in Swollen Syndiotactic Polystyrene F. de Candia,'pt M. Carotenuto,t L. Guadagno,% and V. Vittoriai Dipartimento di Ingegneria Chimica e Alimentare, Universitb di Salerno, Salerno, Italy, Dipartimento di Fisica, Universitit di Salerno, Sakrno, Italy, zyxw and Istituto di Ricerche su Tecnologia dei Polimeri, CNR Arco Felice, Napoli, Italy Received March 9, 1992; Revised Manuscript Received July 20, 1992 ABSTRACT The syndiotactic polystyrene shows a complexpolymorphism,and the structural organization depends on thermal or solventtreatments. The effect of different solventa on oriented samples crystallized in a zigzag conformation haa been investigated,and in some cases a transition to the helix conformation is observed. The obtained results show that the transition occurs through an intermediate amorphous state in which the molecular orientation is maintained. This evidence points to the conclusion that some kind of noncrystalline order is present in the intermediate swollen state. Introduction The syndiotactic polystyrene (sPS) shows a complex polymorphism, and different crystalline forms can be obtained,depending on thermaland/or solventtreatments. Two forms characterized by a zigzag conformation zyxwvu can be obtained by thermal crystallization; one of these, first observed by Ishihara et al.1 and previously indicated as form I,2 is indicated in the more recent literature as the zyxwv a f0rm.3 Its structure has been analyzed by electron diffraction,' and a hexagonal unit cell was suggested. The second form characterized by chains in a zigzag confor- mation, fmt indicated as form 11 : is now definitely indicated as the 6 form.3 The unit cell is orthorhombic,6 and as for the a form the period along the chain axia is 0.51 nm. Two more forms characterized by a helix confor- mation zyxwvutsrq m be obtained by solvent-induced crystalliza- tion?fi17 The period alongthe chain axb is 0.75 nm. These forms, fmt observed by Immini et al.,S are now indicated as the S and 7 forms. They can be obtained by starting from amorphousglassy filme798or by dissolvingthe a form in appropriate solvents.2*6 At variance with the a form, the fi form is stable to the solvent treatments? Zigzag and helix conformations have also been observed in meso- morphic structuresin which the organization is restricted to the conformational and short-range order.l0J1 From this very short picturethe complexnetwork of relationships between structure and thermal and solvent treatments is clearly evident. In the present paper we report further evidence of the great tendency of sPS to arrange different levels of structural Organization. In fact the analysis of the swelling behavior of oriented samples points to the conclusion that some kind of noncrystallineorder is present in the swollen state. Materials and Experimental Section The syndiotactic polystyrene was kindly supplied by Istituto Donegaui of Himont-Italia (Novara, Italy). Glassy fii were obtained according to a previously described procedure, quench- ing to -80 OC the molten sample.? The glassy fi was drawn at two different temperatures wing an extensometer cell and controlling the drawingdegree with reference ink marks. A fit sample, indicated as eample A, was obtained by drawing at 110 "C up to X = 4; a eecond sample, indicated as sample B, was obtained by drawing at 160 OC up to X = 3 (A is the ratio between the final and initial length); a third sample, indicated as sample C, was obtained by annealing sample B 1 h at 180 OC. The + Dipartimentodi Ingegneria Chimica e Alimentare,Universitildi Salemo. t Dipartimento di Fisica, Universita di Salemo. f CNR Arc0 Felice. thickness of the samples after drawing was about 0.02 cm. The structural rearrangements induced by different solvents were analyzed by wide-angle X-ray scattering (WAXS). The solvents used werechloroform,toluene,and tetralin. WAXS was analyzed using a Seifert Debyeflex diffractometer; the radiation was Cu Ka. The sample and swelliig solvents (in large excess) were sealed in a glassy capillarytube and collimated with the X-ray z beam. The diffraction patterns were detected using a flabcamera (6-cm distancefrom the sample). The sample birefringence was evaluated at a qualitative level using an optical microscope. Results (a) Dry Sample Structure. The structural organi- zation of samples A-C, before any solvent treatment, was analyzed by detecting the X-ray diffraction patterns. Samples A shows a diffraction pattern indicative of low structural order; however, a reflection of the first layer is observable, and a period of 0.51 nm along the chain axis can be calculated. In a previous paper, for samples obtained at the same drawing temperature, the experi- mental data suggest the presence of mesomorphic order induced by drawing.12 The organization is restricted mainly to the conformationalorder which is zigzag planar, and a periodicityof 0.51 nm can be detected by the WAXD data. The same period is observed in the two crystalline a and /3 fom.'+J3 Sample B showsthe diffractionpattern of an oriented crystalline system, and the observed reflections are indicative of the a form. In sample C the oriented a form is still present, but the diffraction spots are sharper, indicating better formed and larger crystals. (b) Solvent Treatments. The swellingwith the three solvents gives rise to different effects depending both on the solvent and on the structural organization of the sample. When chloroform is used, any discrete diffraction disappears in less than 1 h, and the sample appears amorphous. The optical microscope, however, indicates the persistence of an appreciable birefringence. This situationremains unchanged until the sampleis immersed in the solvent, also for days. After solvent removal, diffraction of an oriented crystalline system is observed; the reflections are those previously reported for the 6 form,3I8 characterized by a helix conformation with a period along the chain axis of 0.75 nm. The diffraction pattern of sample B after solvent removal is shuown in Figure 1. When tetralin is used as the swelling solvent, the diffraction pattern remains unchanged, and only at very long swelling times, and for sample A only, some weak evidenceof destructurationis observable. It is interesting to note that tetralin induces crystallization in the 6 form 0024-929719212225-6361$03.00/0 Q 1992 American Chemical Society