Carbon-Bridge Incorporation in Organosilicate Coatings Using Oxidative Atmospheric Plasma Deposition

Carbon-bridges were successfully incorporated into the molecular structure of inorganic silicate films deposited onto polymer substrates using an oxidative atmospheric plasma deposition process. Key process parameters that include the precursor chemistry and delivery rate are discussed in the context of a deposition model. The resulting coating exhibited significantly improved adhesion and a 4-fold increase in moisture resistance as determined from the threshold for debonding in humid air compared to dense silica or commercial sol–gel polysiloxane coatings. Other important parameters for obtaining highly adhesive coating deposition on oxidation-sensitive polymer substrates using atmospheric plasma were also investigated to fully activate but not overoxidize the substrate. The resulting carbon molecular bridged adhesive coating showed enhanced moisture resistance, important for functional membrane applications

Heterogeneous Solution Deposition of High-Performance Adhesive Hybrid Films

Interfaces between organic and inorganic materials are of critical importance to the lifetime of devices found in microelectronic chips, organic electronics, photovoltaics, and high-performance laminates. Hybrid organic/inorganic materials synthesized through sol–gel processing are best suited to address these challenges because of the intimate mixing of both components. We demonstrate that deposition from <i>heterogeneous</i> sol–gel solutions leads to the unique nanolength-scale control of the through-thickness film composition and therefore the independent optimization of both the bulk and interfacial film properties. Consequently, an outstanding 3-fold improvement in the adhesive/cohesive properties of these hybrid films can be obtained from otherwise identical precursors

Using Unentangled Oligomers To Toughen Materials

Entanglements between polymer chains are responsible for the strength and toughness of polymeric materials. When the chains are too short to form entanglements, the polymer becomes weak and brittle. Here we show that molecular bridging of oligomers in molecular-scale confinement can dramatically toughen materials even when intermolecular entanglements are completely absent. We describe the fabrication of nanocomposite materials that confine oligomer chains to molecular-scale dimensions and demonstrate that partially confined unentangled oligomers can toughen materials far beyond rule-of-mixtures estimates. We also characterize how partially confined oligomers affect the kinetics of nanocomposite cracking in moist environments and show that the presence of a backfilled oligomeric phase within a nanoporous organosilicate matrix leads to atomistic crack path meandering in which the failure path is preferentially located within the matrix phase

Synthesis of Polyimides in Molecular-Scale Confinement for Low-Density Hybrid Nanocomposites

In this work, we exploit a confinement-induced molecular synthesis and a resulting bridging mechanism to create confined polyimide thermoset nanocomposites that couple molecular confinement-enhanced toughening with an unprecedented combination of high-temperature properties at low density. We describe a synthesis strategy that involves the infiltration of individual polymer chains through a nanoscale porous network while simultaneous imidization reactions increase the molecular backbone stiffness. In the extreme limit where the confinement length scale is much smaller than the polymer’s molecular size, confinement-induced molecular mechanisms give rise to exceptional mechanical properties. We find that polyimide oligomers can undergo cross-linking reactions even in such molecular-scale confinement, increasing the molecular weight of the organic phase and toughening the nanocomposite through a confinement-induced energy dissipation mechanism. This work demonstrates that the confinement-induced molecular bridging mechanism can be extended to thermoset polymers with multifunctional properties, such as excellent thermo-oxidative stability and high service temperatures (>350 °C)