Synthesis of Novel Optically Active Poly(phenyleneethynylene–aryleneethynylene)s Bearing Hydroxy Groups. Examination of the Chiroptical Properties and Conjugation Length

Novel optically active poly­(phenyleneethynylene-aryleneethynylene)­s bearing hydroxy groups with various arylene units [poly­(<b>1</b>–<b>2</b>), poly­(<b>1</b>–<b>3a)</b>, poly­(<b>1</b>–<b>3b</b>), poly­(<b>1</b>–<b>4</b>)] were synthesized by the Sonogashira–Hagihara coupling polymerization of (<i>S</i>)-3,5-diiodo-4-hydroxy-C₆H₄CONHCH­(CH₃)­COOC₁₂H₂₅ (<b>1</b>) with HCC–Ar–CCH [<b>2</b> (Ar = 1,4-phenylene), <b>3a</b> (Ar = 2,7-naphthylene), <b>3b</b> (Ar = 1,4-naphthylene) and <b>4</b> (Ar = 1,6-pyrenylene), and the optical properties were compared. Polymers with number-average molecular weights (<i>M</i>_n) of 5,300–11,300 were obtained in 88–94% yields. CD and UV–vis spectroscopic analysis revealed that all the polymers formed predominantly one-handed helical structures in THF. The order of absorption maxima (λ_max) of the polymers was poly­(<b>1</b>–<b>3a</b>) < poly­(<b>1</b>–<b>2</b>) < poly­(<b>1</b>–<b>3b</b>) < poly­(<b>1</b>–<b>4</b>). Poly­(<b>1</b>–<b>2</b>), poly­(<b>1</b>–<b>3a</b>), poly­(<b>1</b>–<b>3b</b>), and poly­(<b>1</b>–<b>4</b>) emitted blue, purplish blue, green and yellow fluorescence, respectively

Synthesis of Optically Active Conjugated Polymers Bearing <i>m</i>‑Terphenylene Moieties by Acetylenic Coupling Polymerization: Chiral Aggregation and Optical Properties of the Product Polymers

The acetylenic coupling polymerization of d-hydroxyphenylglycine-derived <i>m</i>-terphenylene diynes <b>1</b>–<b>5</b> using Pd/Cu catalyst gave the corresponding polymers [poly­(<b>1</b>)–poly­(<b>5</b>)] with <i>M</i>_n = 12 000–60 000 in 53–89% yields. The polymers were soluble in THF and DMF. CD and UV–vis spectroscopic analysis revealed that <i>p,p</i>′-phenyleneethynylene-linked poly­(<b>1</b>), poly­(<b>3</b>), and poly­(<b>5</b>) formed chiral higher-order structures in THF/H₂O mixtures, while <i>m,m</i>′-phenyleneethynylene-linked poly­(<b>2</b>) and poly­(<b>4</b>) did not. The sign of CD signal of poly­(<b>1</b>) was reasonably predicted by time-dependent density functional calculations of the model system. The polymers emitted fluorescence with quantum yields ranging from 0.2–14.8%

Interplay between Silk Fibroin’s Structure and Its Adhesive Properties

<i>Bombyx mori</i>-derived silk fibroin (SF) is a well-characterized protein employed in numerous biomedical applications. Structurally, SF consists of a heavy chain and a light chain connected via a single disulfide bond. The HC sequence is organized into 12 crystalline domains interspersed with amorphous regions that can transition between random coil/α-helix and beta-sheet configurations, giving silk its hallmark properties. SF has been reported to have adhesive properties and shows promise for development of medical adhesives; however, the mechanism of these interactions and the interplay between SF’s structure and adhesion are not understood. In this context, the effects of physical parameters (i.e., concentration, temperature, pH, and ionic strength) and protein structural changes on adhesion were investigated in this study. Our results suggest that amino acid side chains that have functionalities capable of coordinate (dative) bond or hydrogen bond formation (such as those of serine and tyrosine) might be important determinants in SF’s adhesion to a given substrate. Additionally, the data suggest that fibroin amino acids involved in beta-sheet formation are also important in the protein’s adhesion to substrates

Ligand Exchange Reaction for Controlling the Conformation of Platinum-Containing Polymers

Control of the conformation of polymers can be achieved by the <i>ligand exchange reaction</i> of optically active poly­(phenylene­ethynylene) <b>1′</b> containing −Pt­(PPh₃)₂– moieties in the main chain. Polymer <b>1′</b> was reacted with 1,2-bis­(diphenyl­phosphino)­ethane (dppe), 1,3-bis­(diphenyl­phosphino)­propane (dppp), and 1,4-bis­(diphenyl­phosphino)­butane (dppb) to give the corresponding polymers <b>2′</b>, <b>3′</b>, and <b>4′</b> containing −Pt­(dppe)–, −Pt­(dppp)– , and −Pt­(dppb)– moieties in the main chain, respectively. Polymers <b>1′</b> and <b>2′</b> exhibited negligibly small circular dichroism (CD) signals in THF, indicating the absence of regulated chiral structures, while polymers <b>3′</b> and <b>4′</b> exhibited strong CD signals in THF. The dynamic light scattering (DLS) analysis of the polymer solutions indicated that polymer <b>3′</b> formed a chirally regulated one-handed helix intramolecularly bridged with dppp, and polymer <b>4′</b> formed aggregates intramolecularly and/or intermolecularly bridged with dppb

Sonogashira–Hagihara and Mizoroki–Heck Coupling Polymerizations Catalyzed by Pd Nanoclusters

Sonogashira–Hagihara and Mizoroki–Heck Coupling Polymerizations Catalyzed by Pd Nanocluster