The unit cell of poly-e-caprolactone was found to be orthorhombic with dimensions a = 7.496 + 0.002, b=4.974+0"001, c= 17.297+0-023/~ (fiber axis). The space group is P212121. This unit cell is only compatible with an extended planar chain conformation of the molecule involving two monomer residues related by a twofold screw axis in the chain direction. The P212~2~ space group and the density of 1.146 g.cm-3 indicate that the unit cell contains two chains with opposite orientation ('up' and 'down'). Intensity measurements and structure factor calculations require the rotation of the plane of the chains about their axis to an angle of 28 ° with respect to the a axis; longitudinal chain shift places the ester groups in planes perpendicular to the c axis. Folded chain single crystals with a lancet-like structure were observed by electron microscopy.

Cryomicrotomy of embedded particles, sequential removal of polymeric components via carefully controlled plasma ashing, and a combination of these preparative techniques allowed the microscopic characterization of the internal morphology and chemical composition of inorganic supports, supported catalysts, growing and fully grown polymer particles, and extruded films at submicrometer resolution.Videotaped polymerizations under a microscope at commercially used pressures provided additional insights into the particle growth process. The basic morphological units of polymer growth in olefin polymerizationgrade silicas such as Davison 952 appear to be the intermediate, microspheroidal aggregates of 0.05-0.1 jim diameter. Polymerization initially causes replication of these nodules. The support lattice cracks within the first filling of the pore structure, but the dispersal of the resultant fragments into the submicrometer residues observed in the fully grown polymer particle (15-fold growth) is a more gradual process which is not yet completed after a 5-fold growth of the particle.

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Poly-p-xylylene prepared by the vapor-phase pyrolysis of di-p-xylylene affords a linear high-purity polymer whose crystalline transitions were characterized by x-ray and electron diffraction, mechanical creep studies, and differential thermal analysis (DTA). Two of the three endotherms observed by DTA correspond to the known alpha and beta polymorphs of poly-p-xylylene. The third, occurring at 270°C, is a reversible transition which is regarded as a smectic mesomorphic transition of the stable beta modification. Hence: α→ lim 220∘Cβ1⇋ lim 270∘Cβ2→Tm 420∘C (decomposition).Single crystals precipitated from alpha-chloronaphthalene were instrumental in characterizing the alpha and beta unit cells. The alpha modification is best represented by an orthorhombic cell with a=21.3, b=33.6, c=6.58 Å, for which the theoretical density is 1.141 g·cm−3 at 23°C. The beta modification is hexagonal, with a=20.52±0.05 Å and c=6.581±0.020 Å, having a theoretical density at 23°C equal to 1.153±0.005 g·cm−3. The fiber repeat distance consists of one chemical repeat unit in a fully extended configuration for both modifications. The high positive birefringence, particularly for the beta modification, reveals that the planes of benzene rings in neighboring molecules are steeply inclined to one another.

Tensile stress‐induced crazing in polystyrene, poly(methyl methacrylate), and polycarbonate has been carefully examined by optical and electron microscopy. Examination of the surface of crazed specimens and the cross sections of individual crazes leads to the conclusion that the crazes are not void cracks, but are filled with a craze matter. The craze matter is readily distinguishable from the surrounding resin and is seen to exist in continuity with it. Further experiments confirm the existence of the craze matter and tend to indicate its structural and mechanical properties. These experiments include: microscopic examination of the walls of fractured crazes, micro x‐ray diffraction of craze matter, studies of the strength of crazed specimens under static loads and under increasing tensions, studies of the effect of heat and solvent on crazed specimens, and observations on the ability of crazes to form special networks. The results indicate that the craze matter may be formed by localized resin deformation leading to a load bearing oriented structure. A hypothesis of the mechanism of craze formation is proposed in light of the new and varied information reported in the paper. Study of the kinetics of craze growth suggests the division of the mechanism into three parts: initiation, propagation, and termination. The initiation step describes the concentration of strain energy and the precursory molecular arrangements in the immediate vicinity of inhomogeneities. These are the changes which occur during the time lapse between stress application and first appearance of crazes. The propagation step comprises the sudden and relatively rapid localized resin deformation which creates the craze matter. The shapes of the growing crazes and their diminishing growth rates are attributable to known resin properties. The termination step represents the apparent cessation of craze growth with continued long times of stress application. At this stage in the existence of crazes the proposed hypothesis must blend into the theories of time delayed rupture. It is concluded that stress crazing is basically a molecular slippage rather than a molecular cleavage phenomenon. Considerations, therefore, are to be directed more towards intermolecular forces than intramolecular forces.