M.V. de Paz

Synthesis and characterization of some new homo- and co-poly(vinylsaccharides). Some preliminary studies as drug delivery

Abstract Homopolymers P1 and P3 were prepared by free radical polymerization reactions of 1,3,4,6-tetra- O -acetyl-2-acrylamido-2-deoxy-α- d -glucopyranose monomer ( M1 ) and 1,2:3,4-di- O -isopropylidene-6- O -acryloyl-α- d -galactopyranose monomer ( M2 ), respectively. Both monomers were also copolymerized at two different ( M1 / M2 ) feed ratios (1:1, and 3:1) to yield P4 and P5 , respectively. The free radical polymerization reactions were carried out in a mixed solvent system under either nitrogen atmosphere or vacuum at 60°C using AIBN as free radical initiator. P1 was deacetylated to P2 , while P4 was first deacetylated to P6 and then deacetonated to hydrophilic P7 . The new poly(vinylsaccharides) were characterized by elemental analysis, DSC, GPC, and FT IR, 1 H- and 13 C-NMR spectroscopies. Inherent viscosities and specific optical rotations were also recorded. Some preliminary rheological studies have demonstrated that the hydrophobic, non-swelling acrylic polymer P4 seems to be a good substrate for employment as matrix-forming material for controlled release tablets as drug delivery systems.

A new biodegradable polythiourethane as controlled release matrix polymer

The main aim of this paper is the synthesis and characterization of a new linear functional biodegradable polythiourethane-d,l-1,4-dithiothreitol-hexamethylene diisocyanate [PTU(DTT-HMDI)]. The SeDeM diagram has been obtained to investigate its suitability to be processed through a direct compression process. Furthermore, the ability of this polymer to act as controlled release matrix forming excipient has been studied. Four batches of matrices containing 10-40% of polymer and theophylline anhydrous as model drug have been manufactured. Release studies have been carried out using the paddle method and the polymer percolation threshold has been estimated. The principal parameters of the SeDeM Expert system, such as the parametric profile (mean radius) and the good compression index (IGC=4.59) for the polymer are very close to the values considered as adequate for direct compression even with no addition of flow agents. Furthermore, the results of the drug release studies show a high ability of the polymer to control the drug release. The excipient percolation threshold has been estimated between 20% and 30% w/w of polymer.

Tandem ATRP/Diels–Alder synthesis of polyHEMA-based hydrogels

The efficient, controlled polymerization of a batch of new poly(hydroxyethyl methacrylate-co-furfuryl methacrylate)s, [poly(HEMA-co-FMA)], of various compositions was achieved using atom transfer radical polymerization (ATRP) in methanol. When the FMA composition did not exceed the 10 mol% ratio, the evolution of molecular weight with conversion was linear, and polydispersities were around 1.1 for polymerization reactions at 15 °C and around 1.3–1.4 at 25 °C, indicating good control over the polymerization process. HEMA-based hydrogels were obtained by means of the Diels–Alder reaction between poly(HEMA-co-FMA) and an hydrophilic bisdienophile. Gelification was monitored by diffusion-filtered 1H NMR and solution 1H NMR spectroscopy. Modulated temperature differential scanning calorimetry (MTDSC) suggests the thermo-reversibility of the Diels–Alder coupling reaction of HEMA polymeric networks. Rheological studies showed that the linear viscoelasticity functions of hydrogels were influenced by the chemical composition.