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Broadband dielectric spectroscopy (10 Ϫ2 Hz-10 9 Hz͒ is employed to study the dynamic glass transition of low-molecular-weight glass-forming liquids being confined to nanoporous sol-gel glasses with pore sizes of 2.5, 5.0, and 7.5 nm. As glass-forming liquids, salol ͑one hydroxy group͒, pentylene glycol ͑two hydroxy groups͒, and glycerol ͑three hydroxy groups͒ were chosen. We interpret the dielectric spectra in terms of a two-state model with dynamic exchange between a bulklike phase in the pore volume and an interfacial phase close to the pore wall. This enables one to analyze in detail the interplay between the molecular dynamics in the two subsystems ͑bulklike and interfacial͒, its dynamic exchange, and hence their growth and decline in dependence on temperature and strength of the molecular interactions. For glycerol it is shown that a bulklike dynamic glass transition takes place in subvolumes as small as about 1 nm. ͓S1063-651X͑96͒08711-9͔

Mechanisms for converting electrical energy into mechanical energy are essential for the design of nanoscale transducers, sensors, actuators, motors, pumps, artificial muscles, and medical microrobots. Nanometre-scale actuation has to date been mainly achieved by using the (linear) piezoelectric effect in certain classes of crystals (for example, quartz), and 'smart' ceramics such as lead zirconate titanate. But the strains achievable in these materials are small--less than 0.1 per cent--so several alternative materials and approaches have been considered. These include grafted polyglutamates (which have a performance comparable to quartz), silicone elastomers (passive material--the constriction results from the Coulomb attraction of the capacitor electrodes between which the material is sandwiched) and carbon nanotubes (which are slow). High and fast strains of up to 4 per cent within an electric field of 150 MV x m(-1) have been achieved by electrostriction (this means that the strain is proportional to the square of the applied electric field) in an electron-irradiated poly(vinylidene fluoride-trifluoroethylene) copolymer. Here we report a material that shows a further increase in electrostriction by two orders of magnitude: ultrathin (less than 100 nanometres) ferroelectric liquid-crystalline elastomer films that exhibit 4 per cent strain at only 1.5 MV x m(-1). This giant electrostriction was obtained by combining the properties of ferroelectric liquid crystals with those of a polymer network. We expect that these results, which can be completely understood on a molecular level, will open new perspectives for applications.

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