The Transition and Crystal Transformation of Poly[3,3-bis(chloromethyl)oxacyclobutane] under High Pressure

Abstract

ABSTRACT:The effect of pressure on melting, crystal transformation, and glass transition of poly [3,3-bis(chloromethyl)oxacyclobutane], Penton, has been studied up to 7000 kg/cm2 by the DTA and dilatometric method.The melting temperature-pressure curve for the sample crystallized under high pressure indicates a maximum at about 2800 kg/cm 2, although that for the sample crystallized at atmospheric pressure shows a steady increase with pressure. The sample crystallized under pressure above the maximum point shows a diffused X-ray pattern, the broad melting peak in DTA scan and the positive volume change upon melting in dilatometric measurement. Under pressure above 1800 kg/cm 2 , Penton crystallizes in the p-form, not in the a-form. Further it is observed that the p-form transforms to the a-form by means of annealing at the pressure range of 1800-2000 kg/cm 2 •The pressure dependence of glass transition temperature of Penton is comparatively small, 10-13°Cjl000 kg/cm 2 . After cooling the sample from rubbery state to glassy state under pressure and reducing suddenly the applied p~essure, the subsequent volumetemperature curve shows an anomalous increase around the glass transition temperature, which should be measured at the reduced pressure.KEY WORDS Penton / High Pressure / Melting Temperature Maximum / Crystal Transformation / DTA / Dilatometric Method / Glass Transition / Densified Glass / In high polymers, remarkable effects of pressure appear under a relatively low-pressure region, so that many investigations on high polymers under pressure have been undertaken and various phenomena which can not be seen at atmospheric pressure have been reported. For example, the formation of the extended-chain structure of polyethylene 1 at 5000 kg/cm 2 and the crystal modification which are stable under high pressure, such as the r-form of isotactic polypropylene2 and the phase III of poly(vinylidene fluoride),3 and the existence and nature of highpressure phase in poly(tetrafluoroethylene)4 have been reported. to as Penton, it has previously been shown to exist in two crystal forms. 5 The a-form is obtained when Penton is cooled slowly from the molten state, and the crystallization from the quenched glassy state yields the p-form. On the effects of the pressure on Penton, Kardos 6 has reported that Penton crystallizes in the pform at 5000 kg/cm 2 • Further, Baer and Kardos 7 have obtained a melting temperature-pressure curve up to 3000 kg/cm 2 by the piston displacement method. The obtained curve shows that the pressure dependence of melting temperature becomes smaller with increasing pressure, so if the measurements of melting temperature are carried out in a higher pressure region (above 3000 kg/cm 2 ), it is expected that the melting temperature maximum will occur in this polymer as in the case of elements. 8 Concerning the On poly[3,3-bis(chloromethyl)oxacyclobutane], -(-CH 2 C(CH2Cl)2-CH20-)-,,, hereafter referred

Thermal analysis

“…DTA was used to investigate transition temperatures of 107 compounds belonging to 10 homoloous series of aromatic anils (57) and DSC was applied to inary mixtures of cholesteryl esters (61). Heats of fusion and transition of cholesteryl methacrylate were measured (146). The phase diagrams of the binary systems myristic acid-stearic acid and lauric acid-stearic acid were generated (165) with DTA and X-ray diffraction, where it was found that the first system formed a complex decomposing at ca.…”