This paper deals with the specific ability of molecularly imprinted polymers (MIPs) to release and/or to retain their template. MIPs for caffeine with various MIP:porogen volume ratios were prepared by a non-covalent route. Formation of a prepolymerization complex between the template and the functional monomer was confirmed by nuclear magnetic resonance and computer simulation. The MIP monoliths were successively grinded, sieved, and dried under vacuum. The morphology of the imprinted particles was investigated by scanning electron microscopy, swelling experiments and nitrogen adsorption. Typical release patterns of as-synthesised MIP particles in solvents can be decomposed in three fractions: initial release ( 0 ), slow release over several hours (Á Release ), permanent retention/encapsulation within the MIP (Á Reservoir ). The effect of MIP:porogen volume ratio (related to the MIP porosity) on the releasing/retaining profiles of the materials has been investigated. Finally, the results were critically compared with the available literature and the applicability of MIP reservoirs is briefly discussed.KEY WORDS: Molecular Imprinting / Polymer Morphology / Controlled Release / Polymer Reservoir / Self-Assembly / Molecular imprinting is an emerging technology, which allows the molecular design of polymeric materials containing highly specific receptor sites with an affinity for target compounds.1-3 Formation of a self-assembled pre-polymerization complex between a template molecule and functional monomers, followed by polymerization with a cross-linker in a porogenic solvent and the subsequent extraction of the template, produces a molecularly imprinted polymer (MIP) possessing specifically sized and shaped cavities capable of molecular recognition. 4,5 MIPs are generally highly crosslinked thermosets, and therefore porosity is a necessary feature of their morphology to allow permeability and transport of templates molecules to the bulk polymer phase.To date, a number of promising applications have been proposed for MIPs. For instance, imprinted polymers are used in chromatography as the stationary phase for separation and isolation of racemates.6,7 A related area is solid-phase extraction, where imprinted polymers are employed as a selective sorbent to concentrate the molecule of interest.8 MIPs are also used in immunoassays-type analyses as synthetic antibody 9 and in catalysis as enzyme mimics. 10,11 In the emerging field of biosensors, MIPs demonstrate a potential as the recognition element, although their performance and selectivity in aqueous systems is still a limiting factor. 12,13The application of desorption properties of MIPs is a relatively new area.14,15 Chromatographic data have shown that the MIP-template dissociation kinetics can be controlled by varying the local environment (MIP composition, solvent. . .). Therefore, it seems feasible that MIPs could form highly specific rate limiting reservoirs releasing active compounds at well-defined rates. Early studies delivered promising results and showe...

No abstract

No abstract

Flip chip interconnection technology has been considered the best solution for high-density packaging of a variety of electronic devices. However, there still remain several technical obstacles. The infrastructures are not perfectly ready for die handlingLissembling, die-quality assurance, and so on.

Moire interferometry technique was applied to the thermo-mechanical analysis of flip-chip packages, Thermal deformatiofis of two kinds of flip-ehip structures. no-underfill and undedi11 flip-chip packages, were studied. The diffbrences of the thermal deformations between the two packages were measured to clarify the efflect ofundedill. The experimental results showed that the underfi11 plays an important rvle to give similar curvatures at the lower side of the silicon chip and the upper side of the substfate. The shear deformation of the solder ball decreased due to the underfill, while the tensile deformation increased,