Properties of copolymers composed of one poly-ethylene-oxide and one polystyrene block

Encoding crystal microstructure and chain folding in the chemical structure of synthetic polymers

The development of robust methodologies to control the solid-state structure of polymeric materials by appropriate design of the macromolecular architecture has a crucial impact on the mechanical properties of these materials. Here, we demonstrate the feasibility of controlling chain folding of polymers by steric interactions only, in contrast to previous attempts aimed at engineering polymer crystallization through hydrogen bonding. In a linear synthetic macromolecule similar to polyethylene, we encoded structural instructions that are translated during a crystallization process to generate a unique, semi-crystalline morphology with structure-controlled crystal thickness of approximately 5 nm that remains constant over a wide temperature range. The molecular code consists of a linear backbone alternating crystallizable, long alkyl sequences of monodisperse sizes separated by short spacers containing side-chains and acting as stops and fold-controlling units. This simple strategy could be used to produce advanced polymeric materials with fine control of the crystalline and amorphous regions.

Capture and detection of a quencher labeled oligonucleotide by poly(phenylene ethynylene) particles

Fluorescence quenching of poly(phenylene ethynylene) (PPE) particles by a Cy-5 labeled oligonucleotide is 2 orders of magnitude more sensitive than direct excitation of the Cy-5 fluorophore.

Macromolecular Colloids of Diblock Poly(amino acids) That Bind Insulin

The diblock polymer poly(l-leucine-block-l-glutamate), bLE, was synthesized by acid hydrolysis of the ester poly(l-leucine-block-l-methyl glutamate). During the hydrolysis reaction the leucine block precipitates from the reaction mixture, forming nanosized particulate structures. These particles can be purified and further suspended in water or in 0.15 M phosphate saline buffer (PBS) to give stable, colloidal dispersions. TEM analysis shows the predominant particle form to be that of platelets with a diameter of 200 nm. Smaller cylindrical or spherical particles form a relatively minor fraction of the sample. After fractionation, analysis shows the platelets to be compositionally rich in leucine, while the spheres are glutamate-rich. (1)H NMR, CD, and X-ray diffraction indicate that the core of the platelets is composed of crystalline, helical leucine segments. The poly(l-glutamate) polyelectrolyte brush extending out from the two faces of the disk stabilizes individual particles from flocculation. At pH 7.4, the nanoparticles (platelets and cylinders) spontaneously adsorb proteins, such as insulin, directly from solution. Partial desorption of the protein in its native configuration can be induced by simple dilution. The reversibility of the insulin-nanoparticle complex is the basis for a potential new delivery system. Copyright 1999 Academic Press.