Fabio Zuluaga

Swelling kinetics and release studies of theophylline and aminophylline from acrylic acid/n-alkyl methacrylate hydrogels

Swelling kinetics and drug release (theophylline and aminophylline) from acrylic acid/n-alkyl methacrylate hydrogels are presented. Swelling rate of xerogels decreases as the alkyl chain length in the hydrogels increases because of the increasing hydrophobicity; however, the equilibrium swelling increases with increasing chain length. Drug release from swollen hydrogels is Fickian. Theophylline release is fairly independent of alkyl chain length whereas aminophylline release is highly dependent of alkyl chain length which suggest steric effects and stronger affinity of the latter with the hydrogels. Drug release from xerogels is also different for theophylline and aminophylline. The release of theophylline from xerogels is diffusion controlled and so, it has only a small dependence on the viscoelastic relaxation of the polymeric matrix. By contrast, release of aminophylline from xerogels is non-Fickian.

RAFT “grafting-through” approach to surface-anchored polymers: Electrodeposition of an electroactive methacrylate monomer

Abstract.The synthesis of homopolymer and diblock copolymers on surfaces was demonstrated using electrodeposition of a methacrylate-functionalized carbazole dendron and subsequent reversible addition-fragmentation chain transfer (RAFT) “grafting-through” polymerization. First, the anodically electroactive carbazole dendron with methacrylate moiety (G1CzMA) was electrodeposited over a conducting surface (i.e. gold or indium tin oxide (ITO)) using cyclic voltammetry (CV). The electrodeposition process formed a crosslinked layer of carbazole units bearing exposed methacrylate moieties. This film was then used as the surface for RAFT polymerization process of methyl methacrylate (MMA), styrene (S), and tert-butyl acrylate (TBA) in the presence of a free RAFT agent and a free radical initiator, resulting in grafted polymer chains. The molecular weights and the polydispersity indices (PDI) of the sacrificial polymers were determined by gel permeation chromatography (GPC). The stages of surface modification were investigated using X-ray photoelectron spectroscopy (XPS), ellipsometry, and atomic force microscopy (AFM) to confirm the surface composition, thickness, and film morphology, respectively. UV-Vis spectroscopy also confirmed the formation of an electro-optically active crosslinked carbazole film with a

Multiple Dynamics of Hydrazone Based Compounds

\pi

2-Bromo-2-methyl-N-(4-nitrophenyl)propanamide

-

6-Bromo-pyridine-2-carbaldehyde phenyl-hydrazone.

\pi^{{\ast}}_{}

2-Bromo-2-methyl-N-p-tolyl-propanamide.

absorption band from 450-650nm. Static water contact angle measurements confirmed the changes in surface energy of the ultrathin films with each modification step. The controlled polymer growth from the conducting polymer-modified surface suggests the viability of combining electrodeposition and grafting-through approach to form functional polymer ultrathin films.

2-Bromo-N-(2-hy-droxy-5-methyl-phen-yl)-2-methyl-propanamide.

Hydrazone derivatives of 2-quinolinecarboxaldehyde and 6-bromo-2-pyridinecarboxaldehyde were synthesized by sequence reactions with hydrazine derivatives. These compounds exhibited E/Z isomerization upon irradiation using a mercury lamp (250 W). The configurational changes were monitored by 1 H nuclear magnetic resonance (NMR), UV-Vis and fluorescence spectroscopy. Data of concentration of the E/Z isomers versus time showed first order kinetics with constants ranging from 0.024 to 0.0799 min−1. The Z isomers were isolated by chromatographic methods and characterized by 1 H NMR, UV-Vis and fluorescence spectroscopy and X-ray diffraction. The Z compounds are stable even in solution for several months. Such stability is due to a thermodynamic stabilization by the formation of an intramolecular hydrogen bond in the Z structure, which is not seen in the E configuration. Furthermore, some of the compounds were used as ligands for various metal centers (Zn2+, Co2+ and Hg2+) and their electronic properties were studied including measurements of cyclic voltammetry. The compounds studied herein allow their use as dynamic systems in dynamic combinatorial chemistry as their properties can be modulated by light, heat and the presence of metal centers. Besides, obtaining a metastable state (Z-isomer) allows the use of these compounds as photo-brakes, and therefore they can be implemented as molecular machines.

2-Bromo-N-(4-chloro-phen-yl)-2-methyl-propanamide.

The title compound, C10H11BrN2O3, exhibits a small twist between the amide residue and benzene ring [the C—N—C—C torsion angle = 12.7 (4)°]. The crystal structure is stabilized by weak N—H⋯O, C—H⋯Br and C—H⋯O interactions. These lead to supramolecular layers in the bc plane.

1,4-Phenylenebis(methylene) bis(9H-carbazole-9-carbodithioate).

The title compound, C12H10BrN3, is essentially planar (r.m.s. deviation of all non-H atoms = 0.0174 Å), with a dihedral angle of 0.5 (2)° between the two aromatic rings. In the crystal, molecules are linked by weak N—H⋯N interactions, forming a zigzag chain running parallel to [001].

2-{[(Dodecylsulfanyl)carbonothioyl]sulfanyl}-2-methylpropanoic acid: a chain of edge-fused R(2)(2)(8) and R(4)(4)(20) rings built from O-H...O and C-H...O hydrogen bonds.

In the title molecule, C11H14BrNO, there is twist between the mean plane of the amide group and the benzene ring [C(=O)—N—C C torsion angle = −31.2 (5)°]. In the crystal, intermolecular N—H⋯O and weak C—H⋯O hydrogen bonds link molecules into chains along [100]. The methyl group H atoms are disordered over two sets of sites with equal occupancy.