Recycling of Polydicyclopentadiene Enabled with N-Coordinated Boronic Ester Bonds.

In this contribution, the transformation of polydicyclopentadiene (PDCPD) from thermoset into vitrimer is introduced. First, two N-coordinated diboronic diols are successfully synthesized via the reaction of N,N,N-tri(2-hydroxyethyl)amine and/or N,N,N",N"-tetrakis(2-hydroxyethyl)ethylene diamine with 4-(hydroxymethyl) phenylboronic acid and then they are transformed into two N-coordinated cyclic boronic diacrylates. The latter two dienes carrying electron-withdrawing substituents are used for the ring opening insertion metathesis copolymerization (ROIMP) of dicyclopentadiene to afford the crosslinked PDCPD. In the crosslinked PDCPD networks, N-coordinated cyclic boronic ester bonds are integrated. It is found that the as-obtained PDCPD networks displayed the excellent reprocessing properties. In the meantime, the fracture toughness is significantly improved. Owing to the inclusion of N-coordinated cyclic boronic ester bonds, the modified PDCPDs have the thermal stability much superior to plain PDCPD. The results reported in this work demonstrate that PDCPD can successfully be transformed into the vitrimers via the introduction of N-coordinated cyclic boronic ester bonds.

Polyhydroxyurethane and Poly(ethylene oxide) Multiblock Copolymer Networks: Crosslinking with Polysilsesquioxane, Reprocessing and Solid Polyelectrolyte Properties.

This contribution reports the synthesis of polyhydroxyurethane (PHU)-poly(ethylene oxide) (PEO) multiblock copolymer networks crosslinked with polysilsesquioxane (PSSQ). First, the linear PHU-PEO multiblock copolymers were synthesized via the step-growth polymerization of bis(6-membered cyclic carbonate) (B6CC) with α,ω-diamino-terminated PEOs with variable molecular weights. Thereafter, the PHU-PEO copolymers were allowed to react with 3-isocyanatopropyltriethoxysilane (IPTS) to afford the derivatives bearing triethoxysilane moieties, the hydrolysis and condensation of which afforded the PHU-PEO networks crosslinked with PSSQ. It was found that the PHU-PEO networks displayed excellent reprocessing properties in the presence of trifluoromethanesulfonate [Zn(OTf)2]. Compared to the PHU networks crosslinked via the reaction of difunctional cyclic carbonate with multifunctional amines, the organic-inorganic PHU networks displayed the decreased reprocessing temperature. The metathesis of silyl ether bonds is responsible for the improved reprocessing behavior. By adding lithium trifluoromethanesulfonate (LiOTf), the PHU-PEO networks were further transformed into the solid polymer electrolytes. It was found that the crystallization of PEO chains in the crosslinked networks was significantly suppressed. The solid polymer electrolytes had the ionic conductivity as high as 7.64 × 10-5 S × cm-1 at 300 K. More importantly, the solid polymer electrolytes were recyclable; the reprocessing did not affect the ionic conductivity.

Nanocomposites of epoxy with one-dimensional fibrous poly(ε-caprolactam) nanocrystals via crystallization-driven self-assembly.

In this contribution, we reported the preparation of nanocomposites of epoxy with one-dimensional (1D) poly(ε-caprolactam) (PA6) nanocrystals via crystallization-driven self-assembly. First, a novel diblock copolymer composed of poly(ethylene oxide) and poly(ε-caprolactam) subchains (PEO-b-PA6) was synthesized via the anionic ring-opening polymerization (ROP) of ε-caprolactam. It was found that the PEO-b-PA6 diblocks displayed crystallization-driven self-assembly (CDSA) behavior in the selective solvents (e.g., water); the 1D fibrous nanocrystals of PA6 were obtained via CDSA approach. Such a CDSA behavior was utilized to generate 1D fibrous PA6 nanocrystals into epoxy thermosets. In this case, the epoxy precursors were used as the solvent selective for PEO subchain of the diblock. Notably, the 1D fibrous PA6 nanocrystals were generated in the epoxy precursors via the CDSA approach. Upon curing, the nanocomposites (i.e., the nanostructured thermosets containing PA6 nanocrystals) were successfully obtained. It was found that epoxy thermoset was significantly nanoreinforced by the PA6 nanocrystals. In the meantime, the fracture toughness of the materials was significantly improved with the incorporation of 1D fibrous PA6 nanocrystals.

Generation of One-Dimensional Fibrous Polyethylene Nanocrystals in Epoxy Thermosets.

The one-dimensional (1D) polyethylene (PE) nanocrystals were generated in epoxy thermosets via crystallization-driven self-assembly. Toward this end, an ABA triblock copolymer composed of PE midblock and poly(ε-caprolactone) (PCL) endblocks was synthesized via the ring opening metathesis polymerization followed by hydrogenation approach. The nanostructured thermosets were obtained via a two-step curing approach, i.e., the samples were cured first at 80 °C and then at 150 °C. Under this condition, the one-dimensional (1D) fibrous PE microdomains with the lengths up to a couple of micrometers were created in epoxy thermosets. In contrast, only the spherical PE microdomains were generated while the thermosets were cured via a one-step curing at 150 °C. By the use of the triblock copolymer, the generation of 1D fibrous PE nanocrystals is attributable to crystallization-driven self-assembly mechanism whereas that of the spherical PE microdomains follows traditional self-assembly mechanism. Compared to the thermosets containing the spherical PE microdomains, the thermosets containing the 1D fibrous PE nanocrystals displayed quite different thermal and mechanical properties. More importantly, the nanostructured thermosets containing the 1D fibrous PE nanocrystals displayed the fracture toughness much higher than those only containing the spherical PE nanocrystals; the KIC value was even three times as that of control epoxy.

Nanocomposites of Polyhydroxyurethane with POSS Microdomains: Synthesis via Non-Isocyanate Approach, Morphologies and Reprocessing Properties.

In this contribution, we reported the synthesis of a novel trifunctional POSS cyclic carbonate [POSS-3(5CC)]. With a difunctional five-member cyclic carbonate and a trifunctional polyetheramine as the precursor, the nanocomposites of polyhydroxyurethane (PHU) with POSS were synthesized. Transmission electron microscopy (TEM) showed that the nanocomposites of PHUs with POSS were microphase-separated; the spherical POSS microdomains via POSS-POSS interactions were generated with the size of 20~40 nm in diameter. After the introduction of POSS microdomains, the nanocomposites displayed improved thermal and mechanical properties. More importantly, the nanocomposites still displayed the reprocessing properties of vitrimers.

Crosslinked Polydicyclopentadiene Nanoparticles via Ring-Opening Metathesis Polymerization-Induced Self-Assembly Approach.

In this communication, the preparation of crosslinked polydicyclopentadiene (PDCPD) nanoparticles via ring-opening metathesis polymerization (ROMP)-induced self-assembly approach is reported. For the ROMPs, the macromolecular chain transfer agents (Macro-CTAs) are synthesized via the ring-opening polymerization (ROP) of ε-caprolactone (CL) with cis-2-butene-1,4-diol as the initiator. The ROMPs are performed with chloroform, tetrahydrofuran, toluene, 1,4-dioxane, and N,N-dimethylacetamide as the solvents, respectively, which are catalyzed with Grubbs second generation catalyst. It is found that the crosslinked PDCPD nanoparticles are obtained with spherical, cylindrical to planar morphologies, depending on the molecular weights of Macro-CTAs, the concentrations of DCPD and the natures of solvents. The polymerization induced self-assembly (ROMPISA) by the use of a non-norbornene-based macromolecular chain transfer agent provides a new and efficient approach to prepare crosslinked polymer nanoparticles.

Polythiourethanes Crosslinked with Dynamic Disulfide Bonds: Synthesis via Nonisocyanate Approach, Thermomechanical and Reprocessing Properties.

Polythiourethanes (PTUs) crosslinked with dynamic disulfide bonds are synthesized via a nonisocyanate approach. First, a difunctional five-membered cyclic trithiocarbonate (1) is synthesized via the reaction of diglycidyl ether of bisphenol A (DGEBA) with carbon disulfide (CS2 ). Thereafter, the step-growth polymerizations of 1 with α,ω-diamino poly(propylene oxide)s with various molar masses are carried out to obtain a series of linear poly(mercapto thiourethane)s. These linear poly(mercapto thiourethane)s are readily crosslinked upon formation of disulfide bonds, which are generated via radical coupling reaction with the side mercapto groups. These crosslinked PTUs can be tailored into the materials from thermosetting plastics to crosslinked elastomers, depending on the molar masses of α,ω-diamino poly(propylene oxide)s. More importantly, these crosslinked PTUs display excellent reprocessing properties at elevated temperatures, which is attributable to the metathesis reaction of dynamic disulfide bonds.

Investigation of Azobenzene Photoisomerization Effect on Morphologies and Properties of Nanostructured Thermosets Involving Epoxy and a Diblock Copolymer.

This work highlights the effect of azobenzene photoisomerization on the morphologies and properties of the nanostructured thermosets involving epoxy and a diblock copolymer. First, a diblock copolymer composed of poly(ethylene oxide) (PEO) and poly(6-(4-(4-cyanophenylazo)phenoxy)hexyl methacrylate) (PCPHM) was synthesized, and this diblock copolymer was composed of an epoxy-philic block (i.e., PEO) and an azobenzene moiety-beating block (viz., PCPHM). This diblock copolymer was introduced into epoxy to obtain the nanostructured thermosets via reaction-induced microphase separation approach. To control the configuration of azobenzene moieties of the PCPHM block, the curing reactions were performed in the absence and/or presence of ultraviolet (UV) irradiation, respectively. It was found that, without UV irradiation, the PCPHM microdomains were generated with the trans isomers of azobenzene. Under UV irradiation, however, the PCPHM microdomains were formed with the cis configuration of azobenzene moieties. The ultraviolet-visible light (UV-vis) spectroscopy showed that the trans and cis configurations of azobenzene moieties were significantly fixed with the occurrence of curing reactions. The photoluminescent measurements showed that the nanostructured thermosets with trans-azobenzene moieties can emit fluorescence, which was in sharp contrast to those with cis-azobenzene moieties. The results of small-angle X-ray and atomic force microscopy showed that the nanostructured thermosets with trans and cis isomers of azobenzene moieties had quite different morphologies. It was found that the sizes of the PCPHM microdomains with cis configuration of azobenzene moieties were significantly larger than those with trans configuration. The difference in configuration of azobenzene moieties also resulted in the difference in glass-transition temperatures and dielectric properties of the materials. The results suggest a new approach to modulate the morphologies and physical properties of the nanostructured thermosets by means of photoisomerization of azobenzene moieties.

Fluorescence Enhancement Induced by Curing Reaction in Nanostructured Epoxy Thermosets Containing a Diblock Copolymer.

In this work, a novel curing-induced fluorescence (FL) enhancement phenomenon in the nanostructuring process of epoxy thermosets was investigated. Toward this end, a diblock copolymer composed of poly(ethylene oxide) and poly(((4-vinylphenyl)ethene-1,1,2-triyl)tribenzene) (PTPEE) blocks was introduced into epoxy thermosets. Before curing reaction, the mixtures of epoxy precursors with the diblock copolymer only emitted feeble FL under ultra-visible (UV) irradiation. However, photoluminescence was significantly enhanced after the curing reaction was carried out. It was found that the novel FL enhancement phenomenon resulted from the aggregation-induced emission behavior of PTPEE blocks, which was triggered by curing reaction. In the nanostructured thermosets, the fluorophore blocks (viz. PTPEE) of this diblock copolymer were segregated into aggregates, that is, a reaction-induced microphase separation occurred. Owing to the generation of PTPEE microdomains, the epoxy nanocomposites significantly displayed the enhanced dielectric constants due to the promoted contribution from electron polarizations via π-π conjugation in the materials.

Organic-Inorganic Nanocomposites via Self-Assembly of an Amphiphilic Triblock Copolymer Bearing a Poly(butadiene-g-POSS) Subchain in Epoxy Thermosets: Morphologies, Surface Hydrophobicity, and Dielectric Properties.

Organic-inorganic nanocomposites composed of polyhedral oligomeric silsesquioxane (POSS) and epoxy resin were prepared via self-assembly of an amphiphilic triblock copolymer bearing a poly(POSS) midblock in epoxy thermosets. First, this organic-inorganic amphiphilic triblock copolymer was synthesized via hydrosilylation of heptaphenylhydro POSS with an existing triblock copolymer containing a short polybutadiene midblock. It was found that this novel amphiphilic block copolymer can self-assemble into nanophases in epoxy thermosets. In the presence of preformed nanophases, the curing reaction was performed, and the organic-inorganic nanocomposites containing poly(POSS) microdomains were thus obtained. Compared with plain epoxy, the as-obtained thermosets exhibited enhanced surface hydrophobicity; the enhanced surface hydrophobicity is attributed to enrichment of the POSS component at the surface of the materials. Owing to the formation of poly(POSS) microdomains, the dielectric constants of the materials significantly reduced, whereas the dielectric loss remained almost unchanged.

Dielectric constant enhancement of epoxy thermosets via formation of polyelectrolyte nanophases.

Poly(ethylene oxide)-block-poly(sodium p-styrenesulfonate) (PEO-b-PSSNa) diblock copolymer was synthesized and then incorporated into epoxy to obtain the nanostructured epoxy thermosets containing polyelectrolyte nanophases. This PEO-b-PSSNa diblock copolymer was synthesized via the radical polymerization of p-styrenesulfonate mediated with 4-cyano-4-(thiobenzoylthio)valeric ester-terminated poly(ethylene oxide). The formation of polyelectrolyte (i.e., PSSNa) nanophases in epoxy followed a self-assembly mechanism. The precursors of epoxy acted as the selective solvent of the diblock copolymer, and thus, the self-assembled nanostructures were formed. The self-organized nanophases were fixed through the subsequent curing reaction. By means of transmission electron microscopy (TEM) and small-angle X-ray scattering (SAXS), the morphologies of the nanostructured epoxy thermosets containing PSSNa nanophases were investigated. In the glassy state, the epoxy matrixes were significantly reinforced by the spherical PSSNa nanodomains, as evidenced by dynamic mechanical analysis. The measurement of dielectric properties showed that, with the incorporation of PSSNa nanophases, the dielectric constants of the epoxy thermoset were significantly increased. Compared to the control epoxy, the dielectric loss of the nanostructured thermosets still remained at quite a low level, although the values of dielectric loss were slightly increased with inclusion of PSSNa nanophases.

Thermoresponse improvement of poly(N-isopropylacrylamide) hydrogels via formation of poly(sodium p-styrenesulfonate) nanophases.

The block copolymer networks composed of poly(N-isopropylacrylamide) (PNIPAM) and poly(sodium p-styrenesulfonate) were synthesized via sequential reversible addition-fragmentation chain transfer (RAFT) polymerization with α,ω-didithiobenzoate-terminated poly(sodium p-styrenesulfonate) (PSSNa) as the macromolecular chain transfer agent. It was found that the block copolymer networks were microphase-separated as evidenced by means of transmission electron microscopy (TEM) and small-angle X-ray scattering (SAXS). In the block copolymer networks, spherical or cylindrical PSSNa microdomains were finely dispersed into continuous PNIPAM matrixes. In comparison with unmodified PNIPAM hydrogel, the nanostructured hydrogels displayed improved thermoresponsive properties. In addition, the swelling ratios of the PSSNa-modified PNIPAM hydrogels were significantly higher than that of plain PNIPAM hydrogel. The improvement of thermoresponse was attributable to the formation of the PSSNa nanophases, which promoted the transportation of water molecules in the cross-linked networks.

Organic-inorganic random copolymers from methacrylate-terminated poly(ethylene oxide) with 3-methacryloxypropylheptaphenyl polyhedral oligomeric silsesquioxane: synthesis via RAFT polymerization and self-assembly behavior.

In this contribution, we report the synthesis of organic-inorganic random polymers from methacrylate-terminated poly(ethylene oxide) (MAPEO) (Mn = 950) and 3-methacryloxypropylheptaphenyl polyhedral oligomeric silsesquioxane (MAPOSS) macromers via reversible addition-fragmentation chain transfer (RAFT) polymerization with 4-cyano-4-(thiobenzoylthio) valeric acid (CTBTVA) as the chain transfer agent. The organic-inorganic random copolymers were characterized by means of (1)H NMR spectroscopy, gel permeation chromatography (GPC) and differential scanning calorimetry (DSC). The results of GPC indicate that the polymerizations were carried out in a controlled fashion. Transmission electron microscopy (TEM) showed that the organic-inorganic random copolymers in bulk were microphase-separated and the POSS microdomains were formed via POSS-POSS interactions. In aqueous solutions the organic-inorganic random copolymers were capable of self-assembling into spherical nanoobjects as evidenced by transmission electron microscopy (TEM) and dynamic laser scattering (DLS). The self-assembly behavior of the organic-inorganic random copolymers was also found to occur in the mixtures with the precursors of epoxy. The nanostructures were further fixed via subsequent curing reaction and thus the organic-inorganic nanocomposites were obtained. The formation of nanophases in epoxy thermosets was confirmed by transmission electron microscopy (TEM) and dynamic mechanical thermal analysis (DMTA). The organic-inorganic nanocomposites displayed the enhanced surface hydrophobicity as evidenced by surface contact angle measurements.

Formation of nanophases in epoxy thermosets containing amphiphilic block copolymers with linear and star-like topologies.

In this work, we investigated the effect of topological structures of block copolymers on the formation of the nanophase in epoxy thermosets containing amphiphilic block copolymers. Two block copolymers composed of poly(ε-caprolactone) (PCL) and poly(2,2,2-trifluoroethyl acrylate) (PTFEA) blocks were synthesized to possess linear and star-shaped topologies. The star-shaped block copolymer composed a polyhedral oligomeric silsesquioxane (POSS) core and eight poly(ε-caprolactone)-block-poly(2,2,2-trifluoroethyl acrylate) (PCL-b-PTFEA) diblock copolymer arms. Both block copolymers were synthesized via the combination of ring-opening polymerization and reversible addition-fragmentation chain transfer/macromolecular design via the interchange of xanthate (RAFT/MADIX) process; they were controlled to have identical compositions of copolymerization and lengths of blocks. Upon incorporating both block copolymers into epoxy thermosets, the spherical PTFEA nanophases were formed in all the cases. However, the sizes of PTFEA nanophases from the star-like block copolymer were significantly lower than those from the linear diblock copolymer. The difference in the nanostructures gave rise to the different glass transition behavior of the nanostructured thermosets. The dependence of PTFEA nanophases on the topologies of block copolymers is interpreted in terms of the conformation of the miscible subchain (viz. PCL) at the surface of PTFEA microdomains and the restriction of POSS cages on the demixing of the thermoset-philic block (viz. PCL).

Nanostructures and surface hydrophobicity of epoxy thermosets containing hepta(3,3,3-trifluropropyl) polyhedral oligomeric silsesquioxane-capped poly(hydroxyether of bisphenol A) telechelics.

Hepta(3,3,3-trifluoropropyl) polyhedral oligomeric silsesquioxane (POSS)-capped poly(hydroxyether of bisphenol A) (PH) telechelics was synthesized via Mannich condensation reaction among 4-aminobutylhepta(3,3,3-trifluoropropyl) POSS, phenolic hydroxyl-terminated poly(hydroxyether of bisphenol A) (PH) and formaldehyde. The POSS-capped PH amphiphile was incorporated into epoxy to access the nanostructures in the thermosets. Atomic force microscopy (AFM) showed that the epoxy thermosets possessed the microphase-separated morphologies. The formation of the nanostructures has been interpreted in terms of the self-assembly behavior of POSS-capped PH telechelics in epoxy thermosets. The glass transition temperatures (T(g)'s) of the nanostructured thermosets were quite dependent on the content of POSS-capped PH telechelics. Static contact angle measurements indicate that the POSS-containing nanocomposites displayed a significant enhancement in surface hydrophobicity as well as reduction in surface free energy. The improvement in surface properties was ascribed to the enrichment of POSS moiety on the surface of the nanostructured thermosets, which was evidenced by X-ray photoelectron spectroscopy (XPS).

Hepta(3,3,3-trifluoropropyl) polyhedral oligomeric silsesquioxane-capped poly(N-isopropylacrylamide) telechelics: synthesis and behavior of physical hydrogels.

Hepta(3,3,3-trifluoropropyl) polyhedral oligomeric silsesquioxane (POSS)-capped poly(N-isopropylacrylamide) (PNIPAAm) telechelics with variable lengths of PNIPAAm midblocks were synthesized by the combination of reversible addition-fragmentation chain transfer polymerization (RAFT) and the copper-catalyzed Huisgen 1,3-cycloaddition (i.e., click chemistry). The POSS-capped trithiocarbonate was synthesized and used as the chain transfer agent for the RAFT polymerization of N-isopropylacrylamide. The organic-inorganic amphiphilic telechelics were characterized by means of nuclear magnetic resonance spectroscopy (NMR) and gel permeation chromatography (GPC). Atomic force microscopy (AFM) shows that all the POSS-capped PNIPAAm telechelics exhibited microphase-separated morphologies, in which the POSS terminal groups were self-assembled into the microdomains and dispersed into the continuous PNIPAAm matrices. The POSS nanodomains could behave as the physical cross-linking sites and as a result the physical hydrogels were formed while these POSS-capped PNIPAAm telechelics were subjected to the solubility tests with water. These physical hydrogels possessed well-defined volume phase transition phenomena and displayed rapid reswelling and deswelling thermoresponsive behavior compared to control PNIPAAm hydrogel.

Poly(acrylic acid)-grafted poly(N-isopropyl acrylamide) networks: preparation, characterization and hydrogel behavior.

Poly(acrylic acid)-grafted poly(N-isopropylacrylamide) co-polymer networks (PNIPAAm-g-PAA) were prepared via the reversible addition-fragmentation transfer (RAFT) polymerization of N-isopropyl- acrylamide (NIPAAm) with trithiocarbonate-terminated PAA as a macromolecular chain-transfer agent in the presence of N,N-methylenebisacrylamide. The PNIPAAm-g-PAA co-polymer networks were characterized by means of Fourier transform infrared spectroscopy, differential scanning calorimetry and small-angle X-ray scattering. It is found that the PNIPAAm-g-PAA co-polymer networks were microphase-separated, in which the microdomains of PNIPAAm-PAA interpolymer complexes were dispersed into the PNIPAAm matrix. The PNIPAAm-g-PAA hydrogels displayed a dual response to temperature and pH values. The thermoresponsive properties of PNIPAAm-g-PAA networks were investigated. Below the volume phase transition temperatures, the PNIPAAm-g-PAA hydrogels possessed much higher swelling ratios than control PNIPAAm hydrogel. In terms of swelling, deswelling and reswelling tests, it is judged that the PNIPAAm-g-PAA hydrogels displayed faster response to the external temperature changes than control PNIPAAm hydrogel. The improved thermoresponsive properties of hydrogels are ascribed to the formation of PAA-grafted PNIPAAm networks, in which the water-soluble PAA chains behave as the hydrophiphilic tunnels and allow water molecules to go through and, thus, to accelerate the diffusion of water molecules.

Rapid deswelling and reswelling response of poly(N-isopropylacrylamide) hydrogels via formation of interpenetrating polymer networks with polyhedral oligomeric silsesquioxane-capped poly(ethylene oxide) amphiphilic telechelics.

Hepta(3,3,3-trifluoropropyl) polyhedral oligomeric silsesquioxane-capped poly(ethylene oxide) telechelics (POSS-capped PEO) were synthesized via click chemistry. The POSS-capped PEO amphiphilic telechelics were incorporated into cross-linked poly(N-isopropylacrylamide) (PNIPAAm) to form the structure of physical interpenetrating polymer networks (IPNs). In the organic-inorganic networks, the POSS terminals of POSS-capped PEO telechelics were self-organized into microdomains to act as the physical cross-linking sites of PEO and the physically cross-linked PEO network was interlocked with the PNIPAAm network. It is identified that the organic-inorganic hydrogels resulting from the PNIPAAm network and the POSS-capped PEO telechelics displayed much faster response rates than the plain PNIPAAm hydrogels in terms of swelling, deswelling, and reswelling tests. The improved thermoresponse of hydrogels has been interpreted on the basis of the formation of the specific supramolecular structures in the hydrogels. The synergism from hydrophobic and hydrophilic components (i.e., POSS domains and PEO chains) is responsible for the improvement of hydrogel properties.

Nanostructures and surface hydrophobicity of self-assembled thermosets involving epoxy resin and poly(2,2,2-trifluoroethyl acrylate)-block-poly(ethylene oxide) amphiphilic diblock copolymer.

Poly(2,2,2-trifluoroethyl acrylate)-block-poly(ethylene oxide) (PTFEA-b-PEO) amphiphilic diblock copolymer was synthesized via the reversible addition-fragmentation transfer polymerization of 2,2,2-triffluroethyl acrylate with dithiobenzoyl-terminated poly(ethylene oxide) as a chain-transfer agent. The amphiphilic diblock copolymer was incorporated into epoxy resin to prepare the nanostructured epoxy thermosets. The nanostructures were investigated by means of atomic force microscopy, small-angle X-ray scattering, and dynamic mechanical analysis. In terms of the miscibility of the subchains of the block copolymer with epoxy after and before curing reaction, it is judged that the formation of the nanostructures follows the mechanism of self-assembly. The static contact angle measurements indicate that the nanostructured thermosets containing PTFEA-b-PEO diblock copolymer displayed a significant enhancement in surface hydrophobicity as well as a reduction in surface free energy. The improvement in surface properties was ascribed to the enrichment of the fluorine-containing subchain (i.e., PTFEA block) of the amphiphilic diblock copolymer on the surface of the nanostructured thermosets, which was evidenced by surface atomic force microscopy and energy-dispersive X-ray spectroscopy.

Nanostructures and surface dewettability of epoxy thermosets containing hepta(3,3,3-trifluoropropyl) polyhedral oligomeric silsesquioxane-capped poly(ethylene oxide).

Hepta(3,3,3-trifluoropropyl) polyhedral oligomeric silsesquioxane (POSS)-capped poly(ethylene oxide) (PEO) was synthesized via the reaction of hydrosilylation between hepta(3,3,3-trifluoropropyl)hydrosilsesquioxane and allyl-terminated PEO. The POSS-capped PEO was characterized by means of Fourier transform infrared (FTIR) and nuclear magnetic resonance (NMR) spectroscopy. The organic-inorganic amphiphile was incorporated into epoxy resin to prepare the organic-inorganic nanostructured thermosetting composites. The morphology of the hybrid composites was characterized with field emission scanning electronic microscopy (FESEM) and transmission electronic microscopy (TEM). The formation of nanostructures was addressed on the basis of miscibility and phase behavior of the sub-components (viz. POSS and PEO chains) of the organic-inorganic amphiphile with epoxy after and before curing reaction. The static contact angle measurements indicate that the organic-inorganic nanocomposites displayed a significant enhancement in surface hydrophobicity as well as reduction in surface free energy. The atomic force microscopy (AFM) showed that there is significant migration of the POSS moiety at the surface of the thermosets. The improvement in surface properties was ascribed to the enrichment of the POSS moiety on the surface of the nanostructured thermosets, which was evidenced by X-ray photoelectron spectroscopy (XPS).