The goal of the National Academies Summer Institute is to change teaching practices in introductory, undergraduate biology courses.

No abstract

Comb polysiloxanes with oligo(oxyethylene) side chains of the type -0(CH2CH20)"CH3 were synthesized from poly(methylsiloxane) and zinc octanoate as catalyst. The comb polymers, abbreviated as PMMS (followed by a number indicating the number of oxygen atoms in the side chain), were characterized by FTIR, NMR ( and ^Si), and GPC. Thermal properties were studied by DSC. A considerable fraction of cyclics was found to be present in the polymers, and redistribution reactions result in comb polymers containing branched trisiloxy units. Side-chain crystallization is observed in all polymers except PMMS-5. Polymers with 5,12, 16, and 22 oxygen atoms in the side chain are water-insoluble, but PMMS-8 was soluble enough to carry out cloud-point measurements in the presence of salts.

Polysiloxanes with oligo‐oxyethylene side chains of the type —O(CH2CH2O)7CH3 and —(CH2)3O(CH2CH2O)nCH3 (average n ≈ 7 and 11) were synthesized from poly(hydrogenmethylsiloxane) and characterized by 1H n.m.r., 29Si n.m.r., i.r. and g.p.c. Cyclic analogues were used as model compounds and synthesized from tetramethylcyclotetrasiloxane. Polymer electrolyte complexes were made from the comb polymers and LiClO4 by solvent‐casting from THF, and their conductivities measured as a function of temperature and studied by differential scanning calorimetry and correlated with their conductivity behaviour. Maximum conductivities close to 10−4S cm−1 were achieved at room temperature and at ethylene oxide units to Li+ ratios of about 25. Cross‐linking or blending with high molecular weight poly(oxyethylene) lowers the conductance somewhat but vastly improves the mechanical properties of the complexes, and the blends with PEO can be cast into thin, flexible and tough films with good conducting properties.