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The molecular and crystal structures of the synthesized racemic poly-(,8-ethyl-,8-propiolactone) [-CH(C2Hs)CH2COO-]n were studied by X-ray diffraction. The unit cell is orthorhombic, P212121(Di), with a=9.32A., b=10.02A., and c(fiber axis)= 5.56A.; two molecules pass through the unit cell. The molecule has a conformation

Mathematical expressions for the conformations of linear polymer chains with glide, helical, and translational symmetries were derived, which are represented only by independent internal rotation angles about skeletal bonds: ( k -1) for glide or helical symmetry and ( k -3) for translational symmetry only, k being the number of the main chain atoms in the structural unit. For each symmetry, the remaining internal rotation angles are expressed as explicit functions of the independent internal rotation angles. Especially for helical symmetry, one of the helical parameters 0 is included as a parameter in the expression of the one remaining internal rotation angle. These equations give simultaneously the space-fixed atomic Cartesian coordinates whose 2 axis coincides with the molecular axis. The applications of the method derived here were made to several polymers: hypothetical models of the polymethylene chain whose translational unit consists of three or four methylene groups, poly(tert -butylethylene oxide), and rubber hydrochloride.For the structure analyses of polymers by the use of Xray diffraction and infrared and Raman spectroscopic methods and for energy calculations it is indispensable to describe mathematically conformational models which satisfy definite symmetries and fiber identity periods in terms of bond lengths, bond angles, and internal rotation angles.For the case of polymer chains with glide symmetry, Ganis and Temussi derived an analytical procedure for the conformation.' Recently another treatment was reported in this laboratory2 by extending Shimanouchi and Mizushima's mathematical treatment^.^ For models of helical polymers, there are mathematical equations derived by Shimanouchi and Mizushima3 and improved by M i y a~a w a .~ According to these papers the helical parameters, i e . , the translation along the helix axis per structural unit d and the rotation angle about the helix axis per structural unit 0, are given explicitly by the equations in terms of bond lengths, bond angles, and internal rotation angles. Moreover Sugeta and Miyazawa reformed the equations to matrix formulas which should be suitable for the electronic c~m p u t e r .~ We derived new mathematical equations which can clarify the relationship between the internal coordinates and the conformational parameters. The methods reported in the present paper are applicable to every case of glide, helical, and translational symmetries. In the practical applications of the foregoing methods for each symmetry, the model settings must be carried out by varying all k internal rotation angles with respect to main chain atoms in the structural unit, where the number of main chain atoms in the structural unit is k and the bond lengths and bond angles are held fixed. However, in the present method, the number of variable internal rotation angles is (h-1) for polymers with glide or helical symmetry and (k -3) for the case of translational symmetry only. Therefore the present method reduces the amount of calculation and is especially favorab...

SynopsisThe tensile behaviors of polystyrene (PS), poly(styrene/acrylonitrile) (SAN), high-impact polystyrene (HIPS), and poly(acrylonitrile/butadiene/styrene) (ABS) were examined systematically in the wide range of strain rate, 1.7 X 10-4-13.1 m/s. When glassy and brittle PS was a criterion, the incorporation of a polar group (SAN) only strengthened the hardness, and the fracture mode was the same as for PS. The introduction of dispersed rubber particles (HIPS) weakened the hardness a little but offered a new deformation mechanism, i.e., microcrazing (whitening), and contributed to the improvement of impact strength. In the heterogeneous system, the enhancement of matrix strength [e.g., preorientation or blending with poly(pheny1ene oxide) for HIPS] makes possible another deformation mechanism, i.e., shear band formation (cold drawing), which is superior to microcrazing for achieving higher impact strength, ABS, which incorporates concurrently two factors (polar group to matrix phase and dispersed rubber particles), can be regarded as an enhancement of the matrix strength of HIPS, In spite of the remarkable magnitude of its impact strength compared with that of the other three polymers, the deformation mechanism of ABS was limited to microcrazing. This indicated that only the introduction of a polar group (as nitrile group) could not strengthen the matrix as much as preorientation or blending with poly(pheny1ene oxide). INTRODUCTIONThe homopolymer of styrene (PS) exhibits brittle fracture and low impact toughness at room temperature. To make up for this deficiency, two measures are taken. First, the breaking stress is reinforced by the introduction of polar groups. For example, styrene and acrylonitrile are copolymerized (SAN). Secondly, the strain up to fracture is increased without an accompanying lowering of strength. This can be performed by the addition of rubber in particle form to polystyrene. It is important that the dispersed rubber particles are grafted onto polystyrene chains (not a simple milling-in of rubber with PS matrix). Poly(acrylonitrile/butadiene/styrene) (ABS) is a two-phase material consisting of elastomer particles in a glassy polymer matrix of SAN. ABS can be interpreted as a polymer in which the two measures described above are combined.Correlations among the chemical components of PS, SAN, HIPS, and ABS are schematized (Fig. 1).The aim of the present study is to investigate how the mechanical properties of a polymer change (1) by the introduction of a polar group, (2) with the incorJournal of Applied Polymer Science, Vol. 28,2209Vol. 28, -2216Vol. 28, (1983 poration of dispersed rubber particles which are grafted onto the matrix polymer chains, and (3) by the concurrent introduction of the factors (1) and (2), when polystyrene is primarily a criterion of the mechanical properties. The mechanical testing was limited to measurements of tensile and impact tensile properties at room temperature, where the shape of specimen and the deformation mode were all the same in the wide range of de...