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2‐Methacrylamido‐3‐arylpropionic acid, where aryl is 1‐naphthyl (M1NpPA), 2‐naphthyl (M2NpPA), or 1‐pyrenyl (M1PyPA), was synthesized. Free radical polymerization gave polymers which were soluble in water at pH > 6. In aqueous solution, poly(M1NpPA) and poly(M2NpPA) exhibited strong excimer fluorescence as a dominant component, whereas poly(M1PvPA) showed weak monomer fluorescence as a main component. Excitation spectra and fluorescence quenching by Tl+ ions suggested that naphthyl groups in poly(M1NpPA) and poly(M2NpPA) interacted so as to form excimer sites, by which migrating excited singlets were trapped, leading to the strong excimer emission. It was suggested, however, that pyrenyl groups in poly(M1PyPA) were sterically so constrained that they could not attain the full‐overlap excimer conformation but could only interact to form self‐quenching sites, to which energy migration occurred, leading to weak fluorescence. © 1993 John Wiley & Sons, Inc.

Highly conjugated monomers, 7,7,8,8-tetrakis(alkoxycarbonyl)quinodimethanes (methoxy (1a), ethoxy (1b), isopropoxy (1c), benzyloxy (1d), chloroethoxy (1e), and bromoethoxy (1f)), were synthesized. Recrystallizations of 1a, 1c, 1e, and 1f yielded two crystal forms (prisms (1a-A) and needles (1a-B), needles (1c-A) and plates (1c-B), prisms (1e-A) and plates (1e-B), and prisms (1f-A) and needles (1f-B)), which have different molecular packing modes by X-ray crystal structure analysis, indicating that the crystals are polymorphic. In the photopolymerizations of these monomer crystals in the solid state, 1a-A, 1e-A, and 1f-A polymerized topochemically to give crystalline polymers. For their thermal polymerizations in the solid state, in addition to 1a-A, 1e-A, and 1f-A, 1e-B and 1f-B polymerized, but polymers formed from the 1e-B and 1f-B were amorphous. The packing of quinodimethane molecules in the crystals was defined by four kinds of parameters, stacking distance (d(s)), the distance between the reacting exomethylene carbon atoms (d(cc)), the angles formed between the stacking axis and longer axis of the monomer molecule (theta(1)), and the shorter axis of the monomer molecule (theta(2)), and then the polymerization reactivity of these quinodimethanes in the solid state was discussed on the basis of these parameters.

The difference in the crystal‐packing mode of a monomer can significantly affect its polymerization reactivity. Synthesis of 7,7,8,8‐tetrakis(methoxycarbonyl)quinodimethane (1) afforded two polymorphs: prisms (1 a), and needles (1 b). The former, 1 a, polymerized topochemically under thermal polymerization and photopolymerization (see scheme) but 1 b did not.

Polymer electrolyte membrane fuel cells ͑PEMFCs͒ have been recently investigated extensively as a key technology to solve a global energy and environmental problem by their higher energy conversion efficiency compared to internal combustion engines. The electrolyte membrane is a basic element in PEMFC, however, the polymer electrolyte membrane, typically such as Nafion, usually suffers from degradation at higher temperature, resulting in narrow operational temperature windows below 100°C. If there is an alternative polymer membrane with high stability and sufficient protonic conductivity in the temperature range above 100°C, an intermediate temperature operated PEMFC can be realized which can potentially overcome major problems in the current system such as CO poisoning on the Pt surfaces: large amount of Pt metals at both electrodes and heat management. Additionally, direct methanol fuel cells ͑DMFCs͒ can be feasible at intermediate temperature operation. In this work, sol-gel processes have been used to synthesize a new family of polymer electrolyte membrane consisting of organic/inorganic nanohybrid macromolecules. The flexible, homogeneous, and large-sized hybrid polymer membrane has been found to be thermally stable up to 250°C and to have protonic conductivities of approximately 10 Ϫ3 to 10 Ϫ2 S/cm from a room temperature to 140°C under a humidified condition. The current membrane is potentially useful in an intermediate temperature-operated advanced fuel cells system. Fuel cells are an extremely attractive energy conversion system for use in many industrial applications due to their inherently higher efficiency and lower emission when compared to that of internal combustion engines. Among several types, PEMFCs has been regarded as a promising option for electric vehicles ͑EV͒ and on-site power generation for its superior efficiency and less environmental impact. However, use the current PEM fuel cells are also restricted by elaborate water management. Also, a major limitation of the cell comes from the Pt anode electrocatalysts which are extremely CO intolerant down to the 5 to 10 ppm level. Intermediate temperature operation PEMFC solves problems of CO poisoning as well as passivation of the Pt electrocatalysts by other condensable species. Moreover, the intermediate temperature operation could eventually allow direct use of low temperature reformable fuels such as methanol in the PEMFC DMFC.In recent years, new class of proton conducting membranes have been investigated elsewhere as polymer electrolytes for PEMFCs. 1-30 Numbers of temperature tolerant polymer materials have been synthesized and protonic conductivity at elevated temperature ranges have been investigated intensively. [13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28][29][30] Organic/inorganic nanohybrids are a remarkable family of isotropic, flexible, amorphous polymeric materials for many industrial applications. 31-39 Besides the novel properties of the hybrid materials, they are synthesized through easy processing route wi...