Miniemulsion polymers as solid support for transition metal catalysts

Developing Catalysts for the Hydrolysis of Glycosidic Bonds in Oligosaccharides Using a Spectrophotometric Screening Assay

In a proof-of-concept study, a method for the empirical design of polyacrylate gel catalysts with the ability to cleave 1→4 α-glycosidic bonds in di- and trisaccharides was elaborated. The study included the synthesis of a 300-gel member library based on two different cross-linkers and 10 acrylate monomers, identification of monomodal gels by dynamic light scattering, and a 96-well plate spectrophotometric screening assay to monitor the hydrolysis of chromophore-free maltose into glucose units. The composition of the matrix of the most efficient catalysts in the library was found to enable CH-π, hydrophobic, and H-bond accepting interactions during the hydrolysis as typically seen in glycosylases. The same gel catalysts allowed the hydrolysis of the trisaccharide maltotriose with a catalytic proficiency of 2 × 106 indicating transition state stabilization during the hydrolysis of 5 × 10-7. The results place the developed gels among the most efficient catalysts developed for the hydrolysis of natural saccharides. The elaborated strategy may lead to catalysts that can transform polysaccharides into valuable synthons in the near future.

The electrospinning of the copolymer of styrene and butyl acrylate for its application as oil absorbent

Electrospun polystyrene materials have been employed as oil absorbents, but they have visible drawbacks such as poor strength at low temperature and unreliable integrity because of brittleness and insufficient cohesive force among fibers. Butyl acrylate can polymerize into flexible chains, and its polymer can be used as elastomer and adhesive material. Thereby it is possible to obtain the material that has better performance in comparison with electrospun polystyrene material through the electrospinning of the copolymer of styrene and butyl acrylate. In this work, a polymer was synthesized through suspension polymerization by using styrene and butyl acrylate as comonomers. The synthesis of the copolymer of styrene and butyl acrylate was verified through dissolution and hydrolysis experimental data; as well through nuclear magnetic resonance spectrometry. The viscous flow activation energy of the solution consisting of copolymer and N, N-dimethylformamide was determined via viscosity method and then adopted to establish the entanglement characteristics of butyl acrylate’s chain segments. Finally, in order to electrospin the copolymer solution into fibrous membrane, the effects of monomer feed ratio and spinning parameters were investigated. The prepared fibrous membrane was found to have a potential use as oil absorbent.

4-(2-Pyridylazo)-resorcinol Functionalized Thermosensitive Ionic Microgels for Optical Detection of Heavy Metal Ions at Nanomolar Level

4-(2-Pyridylazo)-resorcinol (PAR) functionalized thermosensitive ionic microgels (PAR-MG) were synthesized by a one-pot quaternization method. The PAR-MG microgels were spherical in shape with radius of ca. 166.0 nm and narrow size distribution and exhibited thermo-sensitivity in aqueous solution. The PAR-MG microgels could optically detect trace heavy metal ions, such as Cu(2+), Mn(2+), Pb(2+), Zn(2+), and Ni(2+), in aqueous solutions with high selectivity and sensitivity. The PAR-MG microgel suspensions exhibited characteristic color with the presence of various trace heavy metal ions, which could be visually distinguished by naked eyes. The limit of colorimetric detection (DL) was determined to be 38 nM for Cu(2+) at pH 3, 12 nM for Cu(2+) at pH 7, and 14, 79, 20, and 21 nM for Mn(2+), Pb(2+), Zn(2+), and Ni(2+), respectively, at pH 11, which was lower than (or close to) the United States Environmental Protection Agency standard for the safety limit of these heavy metal ions in drinking water. The mechanism of detection was attributed to the chelation between the nitrogen atoms and o-hydroxyl groups of PAR within the microgels and heavy metal ions.

Temperature-Induced Assembly of Monodisperse, Covalently Cross-Linked, and Degradable Poly(N-isopropylacrylamide) Microgels Based on Oligomeric Precursors

A simple, rapid, solvent-free, and scalable thermally driven self-assembly approach is described to produce monodisperse, covalently cross-linked, and degradable poly(N-isopropylacrylamide) (PNIPAM) microgels based on mixing hydrazide (PNIPAM-Hzd) and aldehyde (PNIPAM-Ald) functionalized PNIPAM precursors. Preheating of a seed PNIPAM-Hzd solution above its phase transition temperature produces nanoaggregates that are subsequently stabilized and cross-linked by the addition of PNIPAM-Ald. The ratio of PNIPAM-Hzd:PNIPAM-Ald used to prepare the microgels, the time between PNIPAM-Ald addition and cooling, the temperature to which the PNIPAM-Hzd polymer solution is preheated, and the concentration of PNIPAM-Hzd in the initial seed solution can all be used to control the size of the resulting microgels. The microgels exhibit similar thermal phase transition behavior to conventional precipitation-based microgels but are fully degradable into oligomeric precursor polymers. The microgels can also be lyophilized and redispersed without any change in colloidal stability or particle size and exhibit no significant cytotoxicity in vitro. We anticipate that microgels fabricated using this approach may facilitate translation of the attractive properties of such microgels in vivo without the concerns regarding microgel clearance that exist with other PNIPAM-based microgels.

Non-aqueous microgel particles: synthesis, properties and applications

Microgels are cross-linked polymer latex particles that can form stable colloidal dispersions. Their typical sizes range from 10 to 1000 nm and they can swell in response to their external environment (pH, temperature and solvency). This swelling behaviour is central to many potential applications for microgels. The existing literature is dominated by studies of the properties of aqueous microgel dispersions. In contrast, this review focusses on the development of microgel particles in non-aqueous systems, looking at the challenges of studying these particles as well as their swelling behaviour. The five main mechanisms of producing microgel particles will be discussed and examples of materials used for microgels that swell in non-aqueous solvents will be given. Finally some examples of applications for non-aqueous microgels are given.

Attaching high charge density metal ions to surfaces and biomolecules. Reaction chemistry of hypodentate cobalt diamine complexes

Hypodentate diamine cobalt(III) pentammine complexes [Co(NH3)5(NH2(CH2)(n)NH3)](ClO4)4 (8: a: n = 3; b: n = 4; c: n = 6; d: n = 8) have been synthesized via the reaction of [Co(NH3)5(OTf)](OTf)2 (TfOH = CF3SO3H) with the corresponding diamines. The analogous t-boc protected diamine complexes [Co(NH3)5(NH2(CH2)(n)NHt-boc)](ClO4)3 (7a-d) were prepared in 4-26% yield. Low yields for the formation of 7a-d are due to competing side reactions which also gave [Co(NH3)6](3+). Complexes 7a-d were deprotected using trifluoroacetic acid to give the corresponding hypodentate diamine complexes [Co(NH3)5(NH2(CH2)(n)NH3)](CF3CO2)0.5(ClO4)3.5 (9a-d). HBTU coupling of 8c with N-(t-boc)-L-phenylalanine gave an amino acid functionalized cobalt pentammine complex [Co(NH3)5(NH2(CH2)6NHt-boc)-L-phenylalanine)](ClO4)3 (10). All new complexes were characterized using UV-vis and (1)H NMR spectroscopy, and elemental analysis. Grafting of 8c onto 2.4 mm poly(ethylene-co-acrylic acid) (PEAA) beads was achieved via amide coupling. Complex 8c was coupled to thioctic acid via amide coupling and the resulting cobalt disulfide complex [Co(NH3)5(N-(6-aminohexyl)-5-(1,2-dithiolan-3-yl)pentanamide)](ClO4)3 (11) was attached to 10 nm Au nanoparticles. The amount of cobalt loading onto PEAA beads and Au nanoparticles was determined using ICP-MS and EDX.

A Potentially Polymerizable Heterodinuclear FeIIIZnII Purple Acid Phosphatase Mimic. Synthesis, Characterization, and Phosphate Ester Hydrolysis Studies

An analogue of the purple acid phosphatase biomimetic 2-((bis(pyridin-2-ylmethyl)amino)methyl)-6-(((2-hydroxybenzyl)(pyridin-2-ylmethyl)amino)methyl)-4-methylphenol has been synthesized. The analogue, 2-((bis(pyridin-2-ylmethyl)amino)methyl)-6-(((2-hydroxy-4-(4-vinylbenzyloxy)benzyl)(pyridin-2-ylmethyl)amino)methyl)-4-methylphenol (H2BPBPMPV) possesses a pendant olefin suitable for copolymerization. Complexation with FeIII/ZnII resulted in the complex [FeIIIZnII(BPBPMPV)(CH3COO)2](ClO4), characterized with mass spectrometry, microanalysis, UV/vis, and IR spectrometry. The catalytic activity of the complex toward bis-(2,4-dinitrophenyl) phosphate was determined, resulting in Km of 4.1 ± 0.6 mM, with kcat 3.8 ± 0.2 × 10–3 s–1 and a bell-shaped pH–rate profile with pKa values of 4.31, 5.66, 8.96, the profile exhibiting residual activity above pH 9.5.

Rational synthesis of chiral layered magnets by functionalization of metal simple hydroxides with chiral and non-chiral Ni(II) Schiff base complexes

Synthesis of new heterometallic layered magnets with controlled chirality have been achieved by insertion of chiral and non-chiral salen-type Ni(II) complexes into copper and cobalt layered simple hydroxides.