Transparent Macroporous Polymer Monoliths

Abstract

Free-radical polymerization of trimethylolpropane trimethacrylate (TRIM) was carried out in the presence of a variety of porogens at room temperature, yielding transparent (macro)porous polymer monoliths. N2 BET and surface area and Hg intrusion porosimetry data from the resulting polymers showed a variety of different pore sizes and pore size distributions. In the latter, three distinct maxima at 13, 50-60, and ∼500 nm were found for small pores (<500 nm) whereas the observed pore size maxima for large pores (>500 nm) did not exhibit any regularity. Variation of initiator concentration, ratio of monomer to porogen, polymerization temperature, and cross-linker had no influence in obtaining transparent monoliths. Correlation of the transparency of the monoliths with the refractive index and solubility parameter of the corresponding porogens led to threshold values for the refractive index (1.42) above which, and for the total solubility parameter (∼20 (MPa) 1/2 ) below which, a transparent polymer monolith is generally obtained, if one allows for exceptions. A correlation between pore size distribution and transparency, however, could not be found.

Preparation of methacrylate monoliths

“…The polymerization takes place in initially homogeneous solution until the growing and crosslinked polymer chains precipitate. If the porogen is a good solvent for the final polymer, the phase separation occurs later and the pores are smaller [65,74,75]. Thus, the choice of porogenic solvent must be based on the analysis of solubility parameters (d) of monomer and solvent.…”

Optimized preparation of poly(styrene‐co‐ divinylbenzene‐co‐methacrylic acid) monolithic capillary column for capillary electrochromatography

“…The best peak symmetry and column efficiency was obtained when the proportion of isooctane in porogen is 50%. In fact, the addition of a poorer solvent to the polymerization reaction mixture results in an earlier phase separation of the polymer [7], which not only accelerates the polymerization process, but also increases the mean diameter of the pores [33][34][35]. Since the size of pores within the monolithic material is expected to affect the chromatographic efficiency, the very large pores and voids within the monolith enable the rapid exchange of solvents near the precipitated polymer layer.…”

Rigid Macroporous Polymer Monoliths

“…Sherrington et al [84] have reported progress towards the development of an optical sensor system using molecularly imprinted anisotropic polymer monoliths. A transparent [52] imprinted polymer monolith prepared under standard conditions was irradiated with plane polarized light. Those template molecules that have transition dipole moments oriented parallel to the plane of polarization absorb the light, creating reactive species capable of insertion into the polymer backbone.…”