4 research outputs found
Green Aqueous Surface Modification of Polypropylene for Novel Polymer Nanocomposites
Polypropylene
is one of the most widely used commercial commodity
polymers; among many other applications, it is used for electronic
and structural applications. Despite its commercial importance, the
hydrophobic nature of polypropylene limits its successful application
in some fields, in particular for the preparation of polymer nanocomposites.
Here, a facile, plasma-assisted, biomimetic, environmentally friendly
method was developed to enhance the interfacial interactions in polymer
nanocomposites by modifying the surface of polypropylene. Plasma treated
polypropylene was surface-modified with polydopamine (PDA) in an aqueous
medium without employing other chemicals. The surface modification
strategy used here was based on the easy self-polymerization and strong
adhesion characteristics of dopamine (DA) under ambient laboratory
conditions. The changes in surface characteristics of polypropylene
were investigated using FTIR, TGA, and Raman spectroscopy. Subsequently,
the surface modified polypropylene was used as the matrix to prepare
SiO<sub>2</sub>-reinforced polymer nanocomposites. These nanocomposites
demonstrated superior properties compared to nanocomposites prepared
using pristine polypropylene. This simple, environmentally friendly,
green method of modifying polypropylene indicated that polydopamine-functionalized
polypropylene is a promising material for various high-performance
applications
Photoresponsive Liquid Crystalline Epoxy Networks with Shape Memory Behavior and Dynamic Ester Bonds
Functional
polymers are intelligent materials that can respond to a variety of
external stimuli. However, these materials have not yet found widespread
real world applications because of the difficulties in fabrication
and the limited number of functional building blocks that can be incorporated
into a material. Here, we demonstrate a simple route to incorporate
three functional building blocks (azobenzene chromophores, liquid
crystals, and dynamic covalent bonds) into an epoxy-based liquid crystalline
network (LCN), in which an azobenzene-based epoxy monomer is polymerized
with an aliphatic dicarboxylic acid to create exchangeable ester bonds
that can be thermally activated. All three functional building blocks
exhibited good compatibility, and the resulting materials exhibits
various photomechanical, shape memory, and self-healing properties
because of the azobenzene molecules, liquid crystals, and dynamic
ester bonds, respectively
Modified Rheokinetic Technique to Enhance the Understanding of Microcapsule-Based Self-Healing Polymers
A modified rheokinetic technique was developed to monitor
the polymerization
of healing monomers in a microcapsule-based, self-healing mimicking
environment. Using this modified technique, monomers active toward
ring-opening metathesis polymerization (ROMP) were either identified
or disregarded as candidates for incorporation in self-healing polymers.
The effect of initiator loading on the quality and speed of healing
was also studied. It was observed that self-healing polymers have
upper and lower temperature limits between which the healing mechanism
performs at optimal levels. Also, a study of the quality of healing
cracks of different thicknesses was performed, and it was discovered
that above a critical crack thickness value, the quality of self-healing
diminishes substantially; reasons for this phenomenon are discussed
in detail
Controlled Shape Memory Behavior of a Smectic Main-Chain Liquid Crystalline Elastomer
A smectic
main-chain liquid crystalline elastomer (LCE), with controlled
shape memory behavior, is synthesized by polymerizing a biphenyl-based
epoxy monomer with an aliphatic carboxylic acid curing agent. Microstructures
of the LCEs, including their liquid crystallinity and cross-linking
density, are modified by adjusting the stoichiometric ratio of the
reactants to tailor the thermomechanical properties and shape memory
behavior of the material. Thermal and liquid crystalline properties
of the LCEs, characterized using differential scanning calorimetry
and dynamic mechanical analysis, and structural analysis, performed
using small-angle and wide-angle X-ray scattering, show that liquid
crystallinity, cross-linking density, and network rigidity are strongly
affected by the stoichiometry of the curing reaction. With appropriate
structural modifications it is possible to tune the thermal, dynamic
mechanical, and thermomechanical properties as well as the shape memory
and thermal degradation behavior of LCEs