報(bào)告題目：Transformation of a physically crosslinked system into a chemically crosslinked one
報(bào) 告 人：Professor Shaw Ling Hsu（University of Massachusetts (Amherst)）
報(bào)告時(shí)間：2015年5月16日上午9：00
報(bào)告地點(diǎn)：化學(xué)樓二樓一號(hào)會(huì)議室
報(bào)告人簡(jiǎn)介：
Shaw Ling Hsu received his BSc in 1970 from Rutgers University and his PhD in 1975 from University of Michigan. Then, he worked in Allied-Signal Corporation as a research chemist during 1976-1978. In 1978, he joined the Department of Polymer Science and Engineering of University of Massachusetts and has been a full professor since 1987. He was the head of the department during 2003 and 2013. Hsu’s main research interests are the development of environmentally appropriate materials, development of new polymer morphologies for controlled drug delivery, development of multiphase reactive blends, structural characterization of polymer structure in restricted geometry (surfaces/interfaces), deformation behavior of polymers, aging behavior of polymers, residual stress in coatings. He has published over 200 papers including 81 in Macromolecules. Among the awards and honors Hsu received, he won Phi Beta Kappa, Danforth Foundation Fellow, Sigma Xi Honorary Research Society, National Science Foundation Creativity Award, American Physical Society Fellowship, University of Massachusetts Faculty Fellowship, University Outstanding Faculty Leadership Award, USDA National Panel Manager, Bioenergy Production and Byproducts, Chair of Advanced Materials Platform Panel of Taiwan.
報(bào)告簡(jiǎn)介：
A number of applications demand extremely high mechanical properties that cannot be satisfied using ordinary homopolymers. For example cutting tools involve a combination of inorganic particles and a crosslinked polymer matrix. The amount of polymer needed a binder usually is extremely small. One can imagine the exceptional mechanical properties of wet sand versus the dry one. For practical purposes, the polymer matrix usually involving strongly hydrogen bonded component mixed with highly crystalline crosslinkers. In order to complete the reactions, a uniform and continuous dispersion of reactants is necessary. In our study, we have examined the role of plasticizer in the reaction of two seemingly unlikely reactants, highly crystalline hexamethylenetetramine (hexa) and strongly hydrogen bonded phenol formaldehyde resin. By combining information from NMR, infrared spectroscopy and differential scanning calorimetry, we were able to decipher the role of specific intermolecular interactions in order for the plasticizer to dissolve the highly crystalline hexa and to plasticize the phenol formaldehyde resin in this crosslinking reaction. The presence of the plasticizer increased the segmental mobility, disrupted the hydrogen bonded matrix, and freed the hydroxyl units, which further increased the solubility of hexa. Both the endothermic and exothermic transitions are accounted for in the calorimetric data obtained. A complete model describing the reaction has also been achieved. For the first time, it is possible to obtain the effective molar ratio of each component needed to complete the crosslinking reaction efficiently. We have also use this knowledge to elucidate the chain extension reaction involving crystalline salts with reactive polyols.
