A wide band gap polymer derived from 3,6‐carbazole and tetraphenylsilane as host for green and blue phosphorescent complexes

We have synthesized a novel wide band gap polymer P36HCTPSi derived from 3,6‐carbazole and tetraphenylsilane by palladium‐catalyzed Suzuki coupling reaction. The resultant polymer shows a high glass transition temperature (217 °C) and good thermal stability. The conjugation length of P36HCTPSi is effectively confined because of the δ‐Si interrupted polymer backbone. The polymer exhibits a violet emission with a peak at 392 nm in solution, and the band gap estimated from the onset of its absorption is 3.26 eV. The high energy emission and wide band gap of P36HCTPSi make it appropriate host for green and blue emission phosphorescent materials. Efficient energy transfers from P36HCTPSi to both fac‐tris[2‐(2‐pyridyl‐kN)‐5‐methylphenyl]iridium(III) (green emission) and bis[(4,6‐difluorophenyl)pyridinato‐N,C²]‐(picolinato)iridium(III) (blue emission) were observed in photoluminescence (PL) spectra. Highly efficient phosphorescent polymer light‐emitting devices were realized by using P36HCTPSi as the host for iridium complexes, the maximum luminous efficiencies for green and blue devices were 27.6 and 3.4 cd/A, respectively. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 4784–4792, 2009     

Pendant structure governed anion sensing property for sulfonamide‐functionalized poly(phenylacetylene)s bearing various α‐amino acids

The colorimetric detection of anionic species has been studied for α‐amino acid‐conjugated poly(phenylacetylene)s, which were prepared by the polymerization of the ethyl esters of N‐(4‐ethynylphenylsulfonyl)‐L ‐alanine, L ‐isoleucine, L ‐valine, L ‐phenylalanine, L ‐aspartic acid, and L ‐glutamic acid using Rh⁺(2,5‐norbornadiene)[(η⁶‐C₆H₅)B^?(C₆H₅)₃] as the catalyst in CHCl₃. The one‐handed helical conformations of all the sulfonamide‐functionalized polymers were characterized by Cotton effects in the circular dichroism spectra. The addition of anions with a relatively high basicity, such as tetra‐n‐butylammonium acetate and fluoride, induced drastic changes in both the optical and chiroptical properties. On the other hand, anions with a relatively low basicity, such as tetra‐n‐butylammonium nitrate, azide, and bromide, had essentially no effects on the helical conformation of all the sulfonamide‐functionalized polymers. The anion signaling property of the sulfonamide‐functionalized polymers possessing α‐amino acid moieties was significantly affected by the installed residual amino acid structures. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 1683–1689, 2010     

Rotaxane‐type hyperbranched polymers from a crown ether host and paraquat guests containing blocking groups

Rotaxane‐type hyperbranched polymers are synthesized for the first time from A₂B type semi‐rotaxane monomers formed in situ via complexation of bis(m‐phenylene)‐32‐crown‐10 dimethanol ( 1 ) and two paraquat ω‐n‐alkylenecarboxylic acid derivatives with tris(p‐t‐butylphenyl)methylphenylalkylene stoppers ( 8 and 9) . Rotaxane and taco complexes exist in solutions of the hyperbranched polyesters in CD₃CN/CDCl₃ as confirmed by NMR spectroscopy, but the taco complexes, which derive from non‐rotaxanated paraquat units, disappear in DMSO‐d₆. NMR spectroscopy indicates the portion of rotaxanes strongly interlocked by the environment (inner rotaxanes) is larger in HP1?9 , which has longer alkylene spacers, perhaps indicating a higher degree of polymerization. The molecular size increases upon formation of the hyperbranched polymers are confirmed by dynamic light scattering and by viscometry. As with covalent hyperbranched polymers a number of potential applications exist; the unique mechanically linked character and the presence of uncomplexed host and guest moieties foreshadow the use of such systems for their responses to external stimuli with the added benefit of providing molecular recognition sites useful as delivery vehicles. Use of other host‐guest motifs to form the semirotaxane A₂B monomers is possible and complementary systems with higher binding constants will enable efficient syntheses of high molecular weight, mechanically linked hyperbranched polymers. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 1647–1658     

Synthesis and properties of star polymers with a C5‐symmetric bowl‐shaped aromatic core

We report the synthesis and properties of star polymers with a C₅‐symmetric aromatic core. For this, corannulene‐based penta‐substituted polymerization initiators were synthesized. These initiators were then used to polymerize cyclic ester and styrenic monomers via ring opening polymerization and free radical polymerization methods, respectively. Preliminary results suggest that these novel polymers can interact with fullerene, C₆₀, and the degree of interaction can be tuned by the chemical nature of the solvent. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

New materials for optical rectification and electrooptic sampling of ultrashort pulses in the terahertz regime

The synthesis and nonlinear optical characterization of new electrooptic (EO) materials useful for terahertz (THz) applications is presented. Semiempirical calculations were used to guide the development of a series of chromophores on the basis of 2‐dicyanomethylen‐3‐cyano‐4,5,5‐trimethyl‐2,5‐dihydrofuran acceptors acting as guests in polymer films used in the generation of THz radiation via optical rectification. Amorphous films, 65–250 μm thick, with EO coefficients as high as 52 pm/V at 785 nm were used to generate sub‐picosecond pulses with bandwidths up to 3 THz. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 2492–2500, 2003     

Amphiphilic dendritic copolymers of tert‐butyl‐glycidylether and glycidol as a nanocontainer for an anticancer ruthenium complex

Dendritic copolymers comprising a hydrophobic core and hydrophilic shell with nearly equal numbers of hydroxyl groups in the shell and different densities in the core were prepared by a multi‐step process based on anionic ring‐opening polymerization. The diversity in the core density was obtained by using copolymer stars with poly(tert‐butyl‐glycidylether)‐block‐polyglycidol arms with nearly equal length of hydrophobic blocks and numbers of hydroxyl groups of polyglycidol but different numbers of arms as macroinitiators. The ability of the dendritic copolymers to serve as a nanocontainer for a ruthenium complex Ru(NH₃)₃Cl₃ with anticancer properties was studied. The possibility of improving the water solubility of this poorly soluble drug by loading it onto dendritic copolymers was investigated. The hydroxyl groups of the dendritic copolymers were used for complexation of the ruthenium compound to the shell. The loading efficiency was analyzed by UV–vis spectroscopy. The dendritic nanoparticles in their hydrated state were visualized using cryo‐TEM. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 3488–3497     

Supramacromolecular chemistry: Self‐assembly of polystyrene‐based multi‐armed pseudorotaxane star polymers from multi‐topic C60 derivatives

Multitopic dibenzylammonium derivatives ( 4 ) of C₆₀ were prepared by Bingel reactions of C₆₀ with a malonate diester ( 2 ) containing two t‐BOC protected dibenzylamine moieties, followed by deprotection and protonation. Self‐assembly of model pseudorotaxanes 5 from the multidibenzylammonium C₆₀ derivatives with dibenzo‐24‐crown‐8 was studied by ¹H NMR spectroscopy and mass spectrometry. Self‐assembly of linear and star‐shaped pseudorotaxanes 8 with up to 12 arms based on polystyrenes bearing terminal DB24C8 host units ( 7 ) and the guest functionalized C₆₀ salts was demonstrated by ¹H NMR spectroscopy and solution phase viscometry. These studies provide further evidence of the potential of supramacromolecular chemistry in construction of complex polymeric architectures. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 6472–6495, 2009     

Metal‐cation‐induced chiroptical switching for poly(phenylacetylene) bearing a macromolecular ionophore as a graft chain

A poly(phenylacetylene) bearing a polycarbohydrate ionophore as a graft chain (copolymer 4 ) was synthesized by the copolymerization of end‐functionalized (1→6)‐2,5‐anhydro‐3,4‐di‐O‐ethyl‐D ‐glucitol with a 4‐ethynylbenzoyl group (macromonomer 2 ) with phenylacetylene. Copolymer 4 showed a split‐type circular dichroism (CD) in the long absorption region of the conjugated polymer backbone (280–500 nm), and the CD pattern varied in response to external stimuli, such as the solvents and temperature. This suggested that 4 had a predominantly one‐handed helical conformation in the polyacetylene backbone. The CD pattern of 4 was completely inverted by the formation of a complex between the macromolecular ionophore units and the selected metal cations, that is, Ba²⁺, Pb²⁺, Sr²⁺, Na⁺, and Li⁺. This suggested that copolymer 4 underwent a helix–helix transition through the host–guest complexation with achiral inorganic metal cations. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 5855–5863, 2005     

A Peptide‐Cyclodextrin Hybrid System Capable of Detecting Guest Molecules Utilizing Fluorescence Resonance Energy Transfer

Summary: A cyclodextrin‐peptide hybrid bearing coumarin and fluorescein on the peptide side chain has been designed and synthesized as a novel chemosensor molecule utilizing fluorescence resonance energy transfer (FRET). Inclusion of coumarin into β‐cyclodextrin protects this system against fluorescent quenching, so that FRET occurs though donor and acceptor moieties nearby. FRET is diminished upon the addition of various guest compounds, suggesting that this system is useful for detecting molecules in aqueous solution.

A cyclodextrin‐peptide hybrid bearing coumarin and fluorescein on the peptide side chain.     

γ‐Cyclodextrin Derivatives Bearing Thymolphthalein Dyes in Their Secondary Hydroxyl Side as Guest‐Responsive Color Change Indicators

Two geometrically isomeric γ‐cyclodextrin derivatives with a thymolphthalein moiety in the secondary hydroxyl side were prepared as guest‐responsive color change indicators. The isomers exhibit a pH dependence of their absorption spectra and a remarkable change in the absorbance around 610 nm upon guest addition. One of the isomers formed complexes of 2 : 1, the other of 1 : 1 stoichiometry (host/guest).     

Synthesis,characterization, and nucleotidic chain cleavage ability of uncharged water soluble poly(ethylene glycol)‐fullerene derivatives with an amphiphilic character

Water‐soluble fullerenes containing two poly(ethylene glycol) branches [Full‐(PEG)₂] were prepared starting from commercial poly(ethylene glycol)‐monomethyl ethers and C₆₀ [Full‐(PEG)₂]s chemical characterization was made by FT‐IR, NMR, and MALDI‐TOF mass spectrometric analyses. Their thermal stability was determined by TGA experiments. The capability of C₆₀‐derivatives to induce oligonucleotide cleavage under visible light irradiation was also ascertained. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 2154–2153, 2008     

A Smart Polymer with Ion‐Induced Negative Shift of the Lower Critical Solution Temperature for Phase Transition

A novel thermo‐responsive smart copolymer that can selectively respond to specific ions, poly[(N‐isopropylacrylamide)‐co‐(benzo‐15‐crown‐5‐acrylamide)], has been synthesized and characterized. The copolymer exhibits a negative shift of the lower critical solution temperature (LCST) for phase transition that is specifically responsive to certain alkali metal ions. The order of significance of the LCST shift that is induced by ions is K⁺ > Cs⁺ > Na⁺ > Li⁺. The greater the number of crown ether units in the copolymer, or the larger the ion concentration, the higher the sensitivity and selectivity of the copolymer for cation recognition. Because of its novel ion‐responsive characteristics, the proposed smart copolymer is a promising new candidate material for sensors, actuators, switches, and so on.

     

Encapsulation and release by star‐shaped block copolymers as unimolecular nanocontainers

A five‐arm star‐shaped poly(ethylene oxide) (PEO) with terminal bromide groups was used as a macroinitiator for the atom transfer radical polymerization of tert‐butyl acrylate (tBA), resulting in five‐arm star‐shaped poly(ethylene oxide)‐block‐poly(tert‐butyl acrylate) block copolymers. The polymerization proceeded in a controlled way using a copper(I)bromide/pentamethyl diethylenetriamine catalytic system in acetonitrile as solvent. The hydrolysis of the tBA blocks of the amphiphilic star‐shaped PEO‐b‐PtBA block copolymer resulted in dihydrophilic star structures. The encapsulation of the star‐block copolymers and their release properties in acid environment have been followed by UV‐spectroscopy and color changes, using the dye methyl orange as a hydrophilic guest molecule. Characterization of the structures has been done by ¹H NMR, size exclusion chromatography, MALDI‐TOF, and differential scanning calorimetry. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 650–660, 2008     

The accessibility of a unimolecular micelle's core to environmental ions: Exploration with a xanthene dye

To learn the impact of aqueous environmental species on the property of the isolated core of a water‐soluble unimolecular micelle (UIM), a guest dye of erythrosine B (EB) is used as a probe to map the dynamic microenvironment of the UIM. PEGylation of branched polyethylenimine (PEI) with oxirane‐functionalized polyethylene glycol (PEG) leads to a UIM of PEI@PEG, and the core is further chemically engineered. The resulting UIMs can irreversibly encapsulate EB exclusively by the core. It is found that the stacking of EB molecules is dependent on the electronic microenvironment of the UIMs, where a polar and ionic core favors a twist stacking of EB, but a less polar core results in an unprecedented parallel stacking of EB. Spectral analysis shows that EB is encapsulated along with its counter ion of Na+, and an exterior ion can cause dehydration of the UIMs but can hardly enter the UIMs; moreover, ion exchange through the PEG shell is actually allowed. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2015 , 53, 566–573     

Water Soluble Star‐block Copolypeptides: Towards Biodegradable Nanocarriers for Versatile and Simultaneous Encapsulation

The synthesis of water soluble star‐block copolypeptides and their encapsulation properties are described. The star‐block copolypeptides, obtained by ring‐opening polymerization of amino acid N‐carboxyanhydrides, consist of a PEI core, a hydrophobic polyphenylalanine or polyleucine inner shell, and a negatively charged polyglutamate outer shell. The encapsulation study showed that these water soluble, amphiphilic star‐block copolypeptides could simultaneously encapsulate versatile compounds ranging from hydrophobic to anionic and cationic hydrophilic guest molecules.

     

A Tray‐Shaped,PdII‐Clipped Au3 Complex as a Scaffold for the Modular Assembly of [3×n] Au Ion Clusters

A tray‐shaped Pd^II₃Au^I₃ complex ( 1 ) is prepared from 3,5‐bis(3‐pyridyl)pyrazole by means of tricyclization with Au^I followed by Pd^II clipping. Tray 1 is an efficient scaffold for the modular assembly of [3×n] Au^I clusters. Treatment of 1 with the Au^I₃ tricyclic guest 2 in H₂O/CH₃CN (7:3) or H₂O results in the selective formation of a [3×2] cluster ( 1 ? 2 ) or a [3×3] cluster ( 1 ? 2 ? 1 ), respectively. Upon subsequent addition of Ag^I ions, these complexes are converted to an unprecedented Au₃–Au₃–Ag–Au₃–Au₃ metal ion cluster.     

Supramolecular assembly of 2,7-dimethyldiazapyrenium and cucurbit[8]uril: a new fluorescent host for detection of catechol and dopamine

The formation of a highly stable inclusion complex between 2,7-dimethyldiazapyrenium (Me(2)DAP(2+)) and the cucurbit[8]uril host (CB8) was demonstrated by X-ray crystallography; MALDI-TOF mass spectrometry; and (1)H NMR, electronic absorption, and emission spectroscopy. The equilibrium association constant was determined to be 8.9(+/-0.2)x10(5) L mol(-1) from UV-visible data and 8.4(+/-1.5) x 10(5) L mol(-1) from fluorescence data. The Me(2)DAP(2+).CB8 inclusion complex acted as a host to bind compounds containing aromatic pi-donor moieties (D), such as catechol and dopamine. This point was demonstrated by (1)H NMR spectroscopy, and electrochemical and emission measurements. Fluorescence detection of the Me(2)DAP(2+).D.CB8 ternary complexes was evident in aqueous solution and on the surface of silica particles, to which fluorescent diazapyrenium units had been covalently immobilized.     

Pure blue electroluminescent poly(aryl ether)s with dopant–host systems

A series of novel arylene ether polymers (P5F‐BCzVFs) containing both pentafluorene (5F) and distyrylarylene derivative (BCzVF) units in the side chains for efficient pure blue light emission were prepared by a facile, metal‐free condensation polymerization. The emission spectra indicated that color tuning could be achieved through efficient Förster energy transfer from the deep‐blue 5F host to the pure‐blue BCzVF dopant. Single‐layer polymer light‐emitting diodes (PLEDs) based on P5F‐BCzVFs (ITO/(PEDOT:PSS)/polymer/Ca/Al) exhibited voltage‐independent and stable pure blue emission with a Commission International de L'Eclairage (CIE) coordinate of (0.15, 0.15), a maximum brightness of 3576 cd/m², and a maximum luminous efficiencies of 2.15 cd/A, respectively. As most polymers with dopant‐host systems, the luminous efficiencies of all P5F‐BCzVFs surpassed that of the host‐only polymer (P5F), due to the energy transfer and charge trapping from the host to the dopant. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011