5 research outputs found
Simple, Benign, Aqueous-Based Amination of Polycarbonate Surfaces
Polycarbonate
is a desirable material for many applications due
to its favorable mechanical and optical properties. Here, we report
a simple, safe, environmentally friendly aqueous method that uses
diamines to functionalize a polycarbonate surface with amino groups.
The use of water as the solvent for the functionalization ensures
that solvent induced swelling does not affect the optical or mechanical
properties of the polycarbonate. We characterize the efficacy of the
surface amination using X-ray photo spectroscopy, Fourier transform
infrared spectroscopy (FT-IR), atomic force microscopy (AFM), and
contact angle measurements. Furthermore, we demonstrate the ability
of this facile method to serve as a foundation upon which other functionalities
may be attached, including antifouling coatings and oriented membrane
proteins
Controlled Nucleation and Growth of Pillared Paddlewheel Framework Nanostacks onto Chemically Modified Surfaces
The
nucleation and growth of metal–organic frameworks onto
functional surfaces stands to facilitate the utility of these supramolecular
crystalline materials across a wide range of applications. Here, we
demonstrate the solvothermal nucleation and growth of a pillared paddlewheel
porphyrin framework 5 (PPF-5) onto semiconductor surfaces modified
with carboxylic acids. Using versatile diazonium and catechol chemistries
to modify silicon and titania surface chemistries, we show that solvothermally
grown PPF-5 selectively nucleates and grows as stacked crystalline
sheets with preferential (001), (111), and (110) crystallographic
orientations. Furthermore, variations in the synthesis temperature
produce modified stack morphologies that correlate with changes in
the surface-nucleated PPF-5 photoluminescence
Surface Charge Dependent Nanoparticle Disruption and Deposition of Lipid Bilayer Assemblies
Electrostatic interaction plays a leading role in nanoparticle
interactions with membrane architectures and can lead to effects such
as nanoparticle binding and membrane disruption. In this work, the
effects of nanoparticles (NPs) interacting with mixed lipid systems
were investigated, indicating an ability to tune both NP binding to
membranes and membrane disruption. Lipid membrane assemblies (LBAs)
were created using a combination of charged, neutral, and gel-phase
lipids. Depending on the lipid composition, nanostructured networks
could be observed using in situ atomic force microscopy representing
an asymmetrical distribution of lipids that rendered varying effects
on NP interaction and membrane disruption that were domain-specific.
LBA charge could be localized to fluidic domains that were selectively
disrupted when interacting with negatively charged Au nanoparticles
or quantum dots. Disruption was observed to be related to the charge
density of the membrane, with a maximum amount of disruption occurring
at ∼40% positively charged lipid membrane concentration. Conversely,
particle deposition was determined to begin at charged lipid concentrations
greater than 40% and increased with charge density. The results demonstrate
that the modulation of NP and membrane charge distribution can play
a pivitol role in determining NP-induced membrane disruption and NP
surface assembly
Stress Relaxation in Epoxy Thermosets via a Ferrocene-Based Amine Curing Agent
Physical
stress relaxation in rubbery, thermoset polymers is limited
by cross-links, which impede segmental motion and restrict relaxation
to network defects, such as chain ends. In parallel, the cure shrinkage
associated with thermoset polymerizations leads to the development
of internal residual stress that cannot be effectively relaxed. Recent
strategies have reduced or eliminated such cure stress in thermoset
polymers largely by exploiting chemical relaxation processes, wherein
temporary cross-links or otherwise transient bonds are incorporated
into the polymer network. Here, we explore an alternative approach,
wherein physical relaxation is enhanced by the incorporation of organometallic
sandwich moieties into the backbone of the polymer network. A standard
epoxy resin is cured with a diamine derivative of ferrocene and compared
to conventional diamine curing agents. The ferrocene-based thermoset
is clearly distinguished from the conventional materials by reduced
cure stress with increasing cure temperature as well as unique stress
relaxation behavior above its glass transition in the fully cured
state. The relaxation experiments exhibit features characteristic
of a physical relaxation process. Furthermore, the cure stress is
observed to vanish precipitously upon deliberate introduction of network
defects through an increasing imbalance of epoxy and amine functional
groups. We postulate that these beneficial properties arise from fluxional
motion of the cyclopentadienyl ligands on the polymer backbone
Lithographically Defined Three-Dimensional Graphene Structures
A simple and facile method to fabricate 3D graphene architectures is presented. Pyrolyzed photoresist films (PPF) can easily be patterned into a variety of 2D and 3D structures. We demonstrate how prestructured PPF can be chemically converted into hollow, interconnected 3D multilayered graphene structures having pore sizes around 500 nm. Electrodes formed from these structures exhibit excellent electrochemical properties including high surface area and steady-state mass transport profiles due to a unique combination of 3D pore structure and the intrinsic advantages of electron transport in graphene, which makes this material a promising candidate for microbattery and sensing applications