Hydrophobic Building Blocks Research Articles

Efficient and Scalable Synthesis of 4-Carboxy-Pennsylvania Green Methyl Ester: A Hydrophobic Building Block for Fluorescent Molecular Probes.

Fluorinated fluorophores are valuable tools for studies of biological systems. However, amine-reactive single-isomer derivatives of these compounds are often very expensive. To provide an inexpensive alternative, we report a practical synthesis of 4-carboxy-Pennsylvania Green methyl ester. Derivatives of this hydrophobic fluorinated fluorophore, a hybrid of the dyes Oregon Green and Tokyo Green, are often cell permeable, enabling labeling of intracellular targets and components. Moreover, the low pKa of Pennsylvania Green (4.8) confers bright fluorescence in acidic cellular compartments such as endosomes, enhancing its utility for chemical biology investigations. To improve access to the key intermediate 2,7-difluoro-3,6-dihydroxyxanthen-9-one, we subjected bis-(2,4,5-trifluorophenyl)methanone to iterative nucleophilic aromatic substitution by hydroxide on scales of > 40 g. This intermediate was used to prepare over 15 grams of pure 4-carboxy-Pennsylvania Green methyl ester in 28% overall yield without requiring chromatography. This compound can be converted into the amine reactive N-hydroxysuccinimidyl ester in essentially quantitative yield for the synthesis of a wide variety of fluorescent molecular probes.

Multicompartment micelles from silicone-based triphilic block copolymers

An amphiphilic linear ternary block copolymer was synthesised in three consecutive steps via reversible addition–fragmentation chain transfer polymerisation. Oligo(ethylene glycol) monomethyl ether acrylate was engaged as a hydrophilic building block, while benzyl acrylate and 3-tris(trimethylsiloxy)silyl propyl acrylate served as hydrophobic building blocks. The resulting “triphilic” copolymer consists thus of a hydrophilic (A) and two mutually incompatible “soft” hydrophobic blocks, namely, a lipophilic (B) and a silicone-based (C) block, with all blocks having glass transition temperatures well below 0 °C. The triphilic copolymer self-assembles into spherical multicompartment micellar aggregates in aqueous solution, where the two hydrophobic blocks undergo local phase separation into various ultrastructures as evidenced by cryogenic transmission electron microscopy. Thus, a silicone-based polymer block can replace the hitherto typically employed fluorocarbon-based hydrophobic blocks in triphilic block copolymers for inducing multicompartmentalisation.

Carbohydrate‐Modified Silicone Surfactants

AbstractSilicone surfactants have been widely used in our daily life and many industrial fields on the basis of their unusual properties. Only in the past decades has the use of silicone as a hydrophobic building block for the preparation of surfactants become common. The recent trend to combine silicone, polyoxyalkylene and carbohydrate moieties in the same molecule has resulted in a plethora of new compounds with new properties. The generic structure and surface activity of silicone surfactants are reviewed in this article. Especially, the preparation, properties and application of carbohydrate‐modified silicone surfactants such as glucosamide‐containing and glycoside‐containing silicone surfactants are described in detail. In addition, the future development of silicone surfactants is discussed.

Polypropylene Meshes to Prevent Abdominal Herniation. Can Stable Coatings Prevent Adhesions in the Long Term?

Abdominal surgery is associated with a significant risk for incisional herniation. Hernia repair is routinely performed by implantation of synthetic meshes. Such meshes may cause serious adhesions between the implanted material and organs leading to intestinal obstruction or enterocutaneous fistulas. This study compares three knitted meshes for their capacity to prevent adhesion formation in an in vivo study. The meshes evaluated are polypropylene (Prolene), polypropylene coated with oxygenated regenerated cellulose-in principle-a biodegradable biomaterial (Proceed, and Prolene coated with a nondegradable copolymer of the hydrophilic building block N-vinyl pyrrolidone (NVP) and the hydrophobic building block n-butylmethacrylate (BMA). The meshes were implanted in the abdomen of rats (follow-up 7 or 30 days). After 7 days, the formation of adhesions decreased in the order: Prolene > NVP/BMA-coated Prolene > Proceed; after 30 days, this order changed into: Proceed > Prolene > NVP/BMA-coated Prolene. Both at 7 and at 30 days, Proceed was the only mesh surrounded by macrophage cells that contained foreign materials, presumably degradation products of the (biodegradable) surface coating. The data indicate that long-term protection of implanted meshes against excessive adhesions may be achieved through stable biocompatible hydrogel surface coatings.

New Biodegradable Amphiphilic Block Copolymers of ε‐Caprolactone and δ‐Valerolactone Catalyzed by Novel Aluminum Metal Complexes

In our previous study [J. Yang, L. Jia, L. Yin, J. Yu, Z. Shi, Q. Fang, A. Cao, Macromol. Biosci. 2004, 4, 1092.], new biodegradable copolymers of diblock methoxy poly(ethylene glycol)-block-poly(epsilon-caprolactone) and methoxy poly(ethylene glycol)-block-poly(delta-valerolactone), and triblock poly(epsilon-caprolactone)-block-poly(ethylene glycol)-block-poly(epsilon-caprolactone) and poly(delta-valerolactone)-block-poly(ethylene glycol)-block-poly(delta-valero-lactone) bearing narrow molecular weight distributions and well-defined block architectures were reported to be prepared with our original aluminum metal complex templates. This work will continue to report new investigations on their water solubility, and reversible thermal responsive micellization and solution to gel transition in distilled water. Among the new synthesized copolymers (P1-P23), seven diblock or triblock samples (P3, P6, P7, P11, P12, P19, and P21) with higher hydrophilic building block populations were revealed to be water soluble under ambient temperature. By means of UV spectrophotometer attached with a thermostat, important parameters as critical micellization mass concentrations (CMCs) and critical micellization temperatures (CMTs) were characterized for these new amphiphile dilute aqueous solution with the aid of an lipophilic organic dye probe of 1,6-diphenyl-1,3,5-hexatriene (DPH). Furthermore, the critical gelation temperatures (CGTs) were simultaneously investigated for these water-soluble block copolymers via a tube tilting method. It was found that the CMC, CMT, and CGT were strongly affected by the population and nature of the hydrophobic building blocks, and a higher hydrophobicity of the new amphiphilic block copolymer finally led to lower CMC and CMT, and higher CGT. In addition, the salts of KBr and NaCl were found to play as a salt-out effect on the solution to gel transition for the diblock P6 and triblock P11, exhibiting an interesting tunable gelation temperature close to 35-42 degrees C. These results will pave new possibility for the synthesized block structural amphiphiles as potential biomaterials to be applied in vivo.

Synthesis of diblock copolymers with cellulose derivatives. 1. Model study with azidoalkyl carboxylic acid and cellobiosylamine derivative

The basic strategy to make a well-defined A-block-B type cellulose derivative consisting of cellulose and a hydrophobic part was established. The model experiments using cellobiose derivatives play an important role in an actual synthesis of A-block-B type copolymer consisting of cellulose and a hydrophobic part with well-controlled length. A new hydrophobic building block, 15-azidopentadecanoyl chloride, was converted from a commercially available15-hydroxypentadecanoic acid. The novel hydrophobic linker, 15-azidopentadecanoyl chloride, was twice introduced into the reducing end of the cellobiosylamine derivative. The structures of the model compounds for A-block-B type copolymer consisting of sugar and non-sugar blocks were characterized by use of nuclear magnetic resonance (NMR) spectroscopy and Matrix Assisted Laser Desorption/Ionization Time-of-Flight Mass Spectrometry (MALDI-TOF MS).

Block copolymers derived from photoreactive 2-oxazolines, 1. Synthesis and micellization behavior

Amphiphilic block copolymers (BCPs) were synthesized consisting of hydrophilic poly(2-methyl-2-oxazoline) blocks and hydrophobic poly(2-alkyl-2-oxazoline) blocks with undecyl-, phenyl-, and the photopolymerizable cinnamoyl-, 4-azidophenyl-, and diin- moieties. The BCPs were prepared by living cationic ring opening polymerization of the corresponding monomers. The resulting amphiphilic block copolymers show good solubility in water depending on the ratio of hydrophilic to hydrophobic moieties inside the block copolymer as well as the formation of block copolymeric micelles as proven by dynamic light scattering experiments and electron microscopy. The size of the aggregates shows a clear dependence on the polymers molecular weight and the ratio of the hydrophilic to hydrophobic building blocks.

Silicones—Basic chemistry and selected applications

AbstractThe objective of this review is to provide a working knowledge of the chemistry of silicone compounds to the practicing chemist. Although silicone compounds have been known for over 50 yr, the chemistry of these materials remains elusive to the average formulating chemist. This is indeed unfortunate, since the chemistry of the silicon atom and resulting silicone compounds is every bit as wide in scope and rich in content as the chemistry of the carbon atom and the resulting surfactant chemistry upon which it is based. Only in the past decade has the use of silicone as a hydrophobic building block for the preparation of surfactants become common. The recent trend to combine silicone, fatty and polyoxyalkylene moieties in the same molecule has resulted in a plethora of new compounds with new properties.