A new aryl polyester, poly(pentamethylene terephthalate) (PPT) with five methylene groups in the repeat unit, was synthesized. Its multiple‐melting behavior and crystal structure were analyzed with differential scanning calorimetry and wide‐angle X‐ray diffraction. In addition, the spherulitic/lamellar morphology of melt‐crystallized PPT was investigated. Typical Maltese‐cross spherulites (with no rings) were seen in melt‐crystallized PPT at low temperatures (70–90 °C), but ring patterns were seen in PPT crystallized only at temperatures ranging from 100 to 115 °C, whereas rings disappeared with crystallization above 120 °C. The mechanisms of the rings in PPT were explained with several coordinated directional changes (wavy changes, twisting changes, and combinations) in the lamellae during growth. Scanning electron microscopy, in combination with atomic force microscopy, further proved that the ringed spherulites originated from the aggregation of sufficient numbers of edge‐on lamellar crystals; the radial‐growth edge‐on/flat‐on lamellae could be twisted and/or waved to form realistic band patterns. A postulated model properly described a possible origin of the ring bands through combined mechanisms of waving (zigzagging) and twisting (spiraling) of the lamellae during crystallization. Superimposed twisting and/or wavy models during crystallization were examined as examples. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 4421–4432, 2004

ABSTRACT:Experimental and theoretical studies on two ternary blend systems comprised of polystyrene (PS), isotactic polystyrene (iPS) and poly(cyclohexy methacrylate) (PCHMA) or poly(2,6-dimethyl-p-phenylene oxide) (PPO) are described. The differences in phase behavior and morphology of PS/iPS/PCHMA and PS/iPS/PPO ternary blends were investigated and compared by using differential scanning calorimeter (DSC), polarized-light optical microscopy (POM), and scanning electron microscopy (SEM). These two ternary blend systems were found to be completely miscible within the entire composition range at ambient temperature. However, cloud-point transition and LCST behavior was observed for the PS/iPS/PCHMA blend system, but not for the PS/iPS/PPO blend system. Phase diagrams for ternary systems of PS/iPS/PCHMA vs. PS/iPS/PPO at elevated temperatures of cloud points were constructed with the experimental data. Theoretical calculations were found to agree well with the data. Interaction parameters in the PS/iPS/PCHMA vs. PS/iPS/PPO ternary blends were evaluated to assess possible Á among all the binary pairs that constitute these two ternary blends. The melting point depression was used to investigate interactions between pairs of PS/PCHMA vs. PS/PPO, and it was found that asymmetry in the binary interactions led to more ternary phase instability, which was manifested as lowering the LCST and/or cloud points. [DOI 10.1295/polymj.36.909] KEY WORDS Ternary Polymer Blend / Phase Behavior / LCST / PPO / PS / PCHMA / iPS / Truly miscible ternary blends composed of three polymers different in properties may offer a unique opportunity to develop a new polymer material with flexible combination from three constituents. An approach via ternary systems offers more flexibility and better property balancing than what can be achieved by binary blends. Recent advance in studies on ternary polymer blends have resulted in a few more discoveries on miscible ternary blends. The miscibility of ternary polymer blends consisting of three miscible binary pairs has also been studied. [1][2][3][4][5][6] The fact that each binary pair is miscible does not guarantee that all ternary compositions will be. Depending on the interaction parameters of the three binary pairs, the ternary blend system may be completely miscible 3,7,8 or may show an immiscible loop. 9,10 Asymmetry in binary interaction parameters, the so-called Á effect, usually promotes phase separation and enlarges the immiscibility region.9-11 Kwei et al. 12 have reported ternary polymer blends of poly(methyl methacrylate) (PMMA), poly(ethyl methacrylate) (PEMA), and poly(vinylidene fluoride) (PVDF), in which the binary pair of PMMA and PEMA is immiscible; however, the addition of PVDF to the immiscible binary blend PMMA/PEMA can form a miscible ternary blend. Nishi et al. 13 have investigated the phase behavior of ternary polymer blends and analyzed their phase diagrams according to the Flory-Huggins-Scott theory. Ternary blends of PMMA, poly(epichlorohydrin), and PEO are miscible, w...