Synthesis and Self-Assembly of Copolymers with Pendant Electroactive Units

The methacrylic copolymers incorporated with electroactive groups such as thiophene, carbazole, and fluorene moieties on the side chain were synthesized. Our approach consists of incorporating multiple electroactive functional groups onto a polymer backbone that can be used to develop functional materials. All copolymers were characterized, and a systematic structure−property relationship study was established. The structure and morphology of supramolecular self-assembly of copolymers were studied using transmission electron microscopy, wide-angle X-ray diffraction, and atomic force microscopy. Polymers can be patterned using an atomic force microscope, and nanosized lines or dots can be drawn on the polymer films. Polymer nanotubes obtained through self-assembly can be further stabilized by electropolymerization of the side chains

Selective Chain-End Postpolymerization Reactions and Property Tuning of a Highly Conjugated and All-Thiophene Polyazomethine

A highly conjugated polyazomethine (3) consisting uniquely of thiophenes was investigated for sustaining postpolymerization property tuning. This was courtesy of the ever-present and reactive amino and aldehyde chain ends. Subjecting the polymer to polymerization conditions in the absence of monomers resulted in a DPn increase from 15 to 70. The aldehyde chain end was selectively reacted with an aliphatic amine by undergoing reductive amination with sodium triacetoxyborohydride (NaBH(OAc)3) while the imines along the conjugated polymer framework remained intact. This illustrates the robustness of the azomethine bond. Reductive amination of 3 with a monofunctional amine resulted in selective chain-end capping and prevented repolymerization. 3 was resistant to dynamic component exchange and monomer shuffling as a result of its high degree of conjugation. Conversely, chain extension was possible both by reductive amination with an α−ω-diamine and by reheating the polymer. Covalent attachment of two separate segments of 3 was possible by reductive amination with a 2:1 polymer/α−ω-diamine stoichiometry. This resulted in molecular weight doubling and serves to illustrate the possibility of multiblock tethering via the ever-active chain ends. Meanwhile, a 1:1 polymer/α−ω-diamine stoichiometry gave rise to a polymer with an aliphatic and aromatic amine functionalized at either chain end. As a result of the noncomplementary of the two chain ends, the polymer could not be repolymerized. However, it exhibited consistent molecular weight under various repolymerization reaction conditions indicating the robustness of the heteroconjugated bonds and their tolerance toward dynamic component exchange. The color of 3 was also changed from its inherent blue color to green via the covalent attachment of a yellow dansyl derivative by reductive amination at the aldehyde chain end. The collective property modification including repolymerization, coblock tethering, color modification, and increased degree of polymerization presenting unequivocal evidence that polyazomethines are capable of undergoing postpolymerization property tailoring

Photopatternable Electrochromic Materials from Oxetane Precursors

Conjugated thiophenoazomethine triads containing an acid sensitive oxetane group were prepared. The solution processable monomers were immobilized on glass and ITO coated glass substrates by photoacid induced cationic ring-opening polymerization (CROP) of the oxetane moiety. Photolithography using a photoacid generator and photosensitizer were used to pattern an electroactive polymer. Micro- and macroscale patterns ranging between 20 μm and 50 mm were possible with the electrochromic materials. The photopolymerized azomethine remained electroactive, and it could be repeatedly switched electrochemically between its neutral (mauve, λmax = 535 nm) and oxidized (blue, λmax = 585 nm) states without degradation. The electrochromic properties were evaluated in a simulated device where the colors were successfully cycled between blue (oxidized) and purple (neutral) states with applied biases of +0.6 V and −0.6 V vs Fc/Fc+ under ambient conditions without significant color fatigue or degradation

π-Conjugated Fluorescent Azomethine Copolymers: Opto-Electronic, Halochromic, and Doping Properties

A series of new conjugated copolyazomethines consisting of alternating fluorene and thiophenes were prepared. Different thiophenes were incorporated for examining their effect on the polymer’s opto-electronic properties. Blue, red, and green emissions were possible contingent on the thiophene comonomer and the placement of the azomethine nitrogen. Most notably, the polyazomethines were fluorescent both in solution and thin films with measured absolute fluorescent quantum yields (Φfl) ca. 10%. Their fluorescence could be enhanced to near unity at 77 K. High Φfl were also measured with the addition of trifluoroacetic acid (TFA). The polyazomethines’ color could also be reversible altered with protonation/neutralization with TFA/triethylamine. Similar to the halochromic effect, the polyazomethines could be reversibly oxidized/neutralized with FeCl3/hydrazine, resulting in reversible color changes between red and blue. The oxidation potentials and the reversibility of the anodic process were contingent on the type of thiophene incorporated into the copolymer. The stability of the electrochemically produced radical cation and the azomethine’s resistance toward hydrolysis were also investigated with a model thiophene–fluorene–thiophene bisazomethine