The Preparation Of Composites Of Poly(N-isopropy Lacrylamide) With Silica And Its Application In HPLC

In this study thermosensitive composites were prepared through grafting copolymerization of N-isopropylacrylamide with [3-(methacryloyloxy) propyl] trimethoxysilane (MPT, a silicon coupling agent) andγ-Mercaptopropyl triethoxysilane, ( MPS, a silicon coupling agent) coupled on the surface of ultrafine silica beads. The effects of some synthetic conditions such as stabilizers, solvents, initiator, feed ratio on the grafting yields were investigated. The structures of the composites were characterized by infrared spectra, differential scanning calorimetry, and scanning electron microscope. The thermosensitive composite was used as a packing material in high performance liquid chromatography (HPLC) for separating naphthalene derivatives. The result indicated that satisfactory separation was achieved by controlling temperature of the column. As a comparison the packing material of silica-MOPT has no this separating efficiency due to absence of thermosensitivety. The mechanism for the temperature-controlled separation is attributed to polarity change of the PNIPAM on silica surface when PNIPAM undergoes volume phase transition.Additionally the mobile phase composing has large effect on separation. Because a complex structure is formed between methanol and water molecules as methanol increases to a certain content in the mixture. Methanol/ water solution is a poor solvent for PNIPA. The thermosensitivity of PNIPAM is obvious only in aqueous solution. Because water is main component of the mobile phase, the method of separation has many strongpoints of less pollution, lower cost and high efficiency of separation. If the method is used in the separation of bioactive materials such as polypeptides and proteins, it does not kill the activity of the separated materials.Because the main component of mobile phase is water, so the method have the merit of less pollution, low cost, high efficiency in separation. If the system was used in separating the amino acid and protein , it would be propitious to keep the activity of them.