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Epoxy‐amine thermosetting resins undergo different reactions depending on the amine/epoxy stoichiometric ratio (r). Although many desirable properties can be achieved by varying the stoichiometric ratio, the effects of the variation on the crosslinked structure and mechanical properties and the contribution of these factors to the ductility of materials have not been fully elucidated. This study investigates the brittle‐ductile behavior of epoxies with various stoichiometric ratios and performs curing simulations using molecular dynamics (MD) to evaluate the crosslinked structures. The molecular structure is predominantly branched in low‐stoichiometric ratio samples, whereas the chain extension type structure dominates the high‐stoichiometric ratio samples. As a result, the higher‐stoichiometric ratio samples enhances the ductility of materials and the elongation at break increases form 1.4% (r = 0.6) to 11.4% (r = 1.4). Additionally, the tensile strength (105.4 MPa) and strain energy (7.96 J/cm3) are maximum at r = 0.8 and 1.2, respectively. On the other hand, the Young's modulus is negatively impacted and it decreased from 4.2 to 2.7 GPa with increasing stoichiometric ratio.

39) We thank Dr. I. Voigt-Martin for kindly supplying us with the electron micrographs.(40) The previously reported SALS patterns for this series of quenched samples1" indicates that the quenching temperature corresponded to about 70 °C. (41) Our previous report10 suffers from this deficiency, and the enthalpies of fusion are lower than the correct values. This error can be rectified, to a very good approximation, by adding 0.10 to the degree of crystallinities previously calculated from the enthalpy of fusion measurements. (42) It should be noted that the premise of interface-controlled growth makes no assumption or imposes any requirements on the interfacial structure. In particular, identification with a regularly folded interface is unnecessary and incorrect.

Micelle formation and the hydrophobic domain structure of a water-soluble ABA-type block copolymer of hydrophobic poly(2-hydroxyethyl methacrylate) (PHEMA) and hydrophilic polyethylene oxide) (PEO) were investigated by means of small-angle X-ray scattering and a fluorometric analysis using fluorescent dyes as probes for the hydrophobic region. The emission Xm"T of a fluorescent dye added to a block copolymer solution exhibits a distinct two-step blue shift with an increase in polymer concentration. The concentration at which the second transition takes place is consistent with the critical concentration for the intermolecular association determined from light scattering. The first transition in the emission Xmax indicates that the hydrophobic domain of the contracted PHEMA chain was formed within a molecule, suggesting the formation of a monomolecular micelle. Subsequent intermolecular association through PHEMA chains appears to bring about further aggregation of PHEMA chains within the hydrophobic domain. The fluorescence spectra exhibit a remarkable temperature dependence and the emission Xm" was shifted toward shorter wavelength on lowering the temperature in both the monomolecular and polymolecular micelles. As for the polymolecular micelle, X-ray scattering data reveal that a considerable extent of the intermixing phase exists in the interfacial region between the core and the shell and also that the width of the intermixing phase decreases with a lowering of the temperature. This suggests that a demixing of the constituent blocks results in an enhancement of the hydrophobicity of the PHEMA chains within the core of the micelle. The state of the PHEMA chains in the intermixing phase is discussed.