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A homologous series of aliphatic polycarbonates with different side-chain lengths was synthesized by ring-opening polymerization of terminal epoxides with CO 2 using zinc adipionate as catalyst [patented process of Empower Materials (formerly PAC Polymers Inc.)]. Additionally, a polycarbonate was made having a cyclohexane unit in its backbone, together with a terpolymer having both cyclohexane and propylene units. After characterization of thermal properties the aliphatic polycarbonates were found to be completely amorphous. Polycarbonates derived from long-chain epoxides showed a glass-transition temperature (T g ) below room temperature, whereas polycarbonates derived from cyclohexene oxide showed a T g of 105°C, the highest yet reported for this class of polymers. The initial decomposition temperature of the polymers in air and nitrogen atmospheres was found to be less than 300°C. The mechanical properties and the dynamic mechanical relaxation behavior of the polymers were also reported. The effect of the chemical structure on the physical properties of aliphatic polycarbonates was discussed.

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The crystallization behavior of three molecular weight samples of poly(ε‐caprolactone) has been studied as a function of temperature. Crystallization begins in the form of axialities and changes to spherulite growth as time progresses, presumably owing to the molecular weight distribution. Determinations of equilibrium melting point and analyses of growth kinetics are complicated by a major lamellar thickening process occurring at the crystallization temperature. Secondary nucleation analyses of spherulitic growth rates, carried out assuming a similar growth face to that of polyethylene, result in values of σσe. Use of the Thomas–Stavely relation to calculate a value of σ results in values of fold‐surface free energy, σe, similar to that of polyethylene.

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The melting behavior of three representative semirigid polymers, poly(aryl ether ether ketone), poly(ethylene terephthalate), and poly(ethylene naphthalenate), has been studied. Analysis of experimental results indicates that the melting process is morphologically the reverse of the isothermal crystallization process with respect to primary and secondary structural elements. On this basis, it is hypothesized that melting of all three polymers occurs in three distinct steps, assuming that spherulites are composed of dominant lamellae and subsidiary branches. The latter might have originated either from material rejected from the dominant lamellae or from noncrystalline molecular sections in the vicinity of the dominant lamellae. Experimental results emerging from differential scanning calorimetry, polarized optical microscopy, and small-angle X-ray scattering can be explained in terms of such a morphology, for which two possible models are suggested.

The correct value of the equilibrium melting point of isotactic polypropylene has been determined using small-angle X-ray diffraction. The conflict in the literature between the two very different values obtained through extrapolation of melting point versus crystallization temperature data has been resolved.It is demonstrated through studies of the melting point of polypropylene as a function of crystallization time that the dependence of melting point elevation on supercooling is the opposite of that of polyethylene. The thickening process is shown to be most effective at low supercoolings, leading to abnormally high melting points for specimens crystallized at low supercoolings. The equilibrium melting point of isotactic polypropylene is close to 186 °C. It is believed that the observed behavior is a direct result of polypropylene crystallizing in regimes II and III, unlike bulk linear polyethylene, which crystallizes in regimes I and II. It is suggested that the behavior may be directly related to the length of continuous adjacent reentry folding generated under the different regimes.