Biomedical subjects

Michael R Bockstaller

Publications and source records attributed to Michael R Bockstaller.

4 recordsLinked to original sources

PubMed2006

Selectivity- and size-induced segregation of molecular and nanoscale species in microphase-ordered triblock copolymers.

Microphase-ordered block copolymers serve as model systems to elucidate the potential of molecular self-assembly and organic templates to fabricate functionalized polymeric materials. Both aspects are related to the incorporation of secondary species such as low-molar-mass compounds or nanoparticles within the copolymer matrices. Since the resulting properties of such functionalized copolymers critically depend on the morphology of the blend or composite, the nonrandom distribution of such inclusions within the copolymer matrix must be understood. Using a self-consistent field theoretical approach, we quantitatively evaluate the segregation and interfacial excess of low-molar-mass and nanoscale species in ordered triblock copolymers as functions of block selectivity and inclusion size. The predictions are found to agree with the morphology observed in a model triblock copolymer/nanoparticle composite, thereby demonstrating the generality of this approach. Our results suggest a wide correspondence in the structure-forming effect of molecular and nanoscale inclusions that will have implications in the design and processing of functional nanostructured polymers.

Computer Simulation↗

PubMed2005

2D spatially periodic architectures via the drying of 1D holographically photopatterned polymer solutions.

We demonstrate an efficient and versatile method for selectively generating 1D and 2D periodic polymer structures in the submicron to tens of micron range by the directed drying of 1D photopatterned polymer solutions. Ultraviolet (UV) holographic lithography (Xia et al. Chem. Rev. 1999, 99, 1823-1848) is initially used to create 1D periodic cross-link and density variations in the polymer/volatile solvent solutions. These variations act as anisotropic barriers (walls) that direct the subsequent solvent evaporation process. Somewhat akin to directional drying (Allain and Limat Phys. Rev. Lett. 1995, 74, 2981-2984) and directional solidification (Pelc, P. Dynamics of Curved Fronts; Academic Press: San Diego, CA, 1988) experiments, the drying exhibits channel-like interface propagation behavior. The combination of the instabilities and minimization of the interface area during drying can be effectively used to produce larger scale 2D pseudohexagonal polymer-strut structures, or by the addition of a monomeric component to the polymer solution, the instabilities can be suppressed, resulting in the formation of 1D linear gratings.

Journal Article↗

PubMed2004

Proximity effects in self-organized binary particle-block copolymer blends.

Dependent on the surface chemistry of gold nanocrystals of equal metal core size, two morphological types of self-organized block copolymer-particle blends are observed: (1) the segregation of the nanocrystals to the interfacial areas or (2) the preferential uniform distribution within one of the respective polymer domains. The confinement of the nanocrystals to the narrow interfacial regions of the microstructure in type one blends results in high local particle filling fractions and gives rise to electromagnetic coupling upon light irradiation, accompanied by a pronounced increase in absorbance.

Journal Article↗

PubMed2003

Size-selective organization of enthalpic compatibilized nanocrystals in ternary block copolymer/particle mixtures.

Dependent on the relative particle core size, two distinct types of particle topologies in block copolymer/nanocrystal blends have been identified, that is, the localization of particles along the intermaterial dividing surface or at the center of the respective polymer domain. In ternary systems consisting of block copolymer and two different-sized nanocrystal species, the distinct morphological types are conserved, resulting in autonomous size-selective separation and organization of the respective nanocrystals within alternating arrays and sheets.

Journal Article↗