Cyclopolymerization of α,ω‐heterodifunctional monomers containing styrene and maleimide moieties

A series of α,ω‐heterodifunctional monomers with styrene (St) and maleimide moieties bridged by a varied length of oligo‐ethylene glycol (OEG) linkers were synthesized. Cyclopolymerizations of these monomers through reversible addition–fragmentation chain transfer‐mediated alternating radical copolymerization between intramolecular St and maleimide moieties were investigated. For the monomers with three or more ethylene glycol (EG) units, their cyclopolymerizations can be realized properly in low monomer feeding concentrations, affording well‐defined cyclopolymers with crown ether encircled in their main chains. Importantly, the cyclopolymerizations of monomers with six or seven EG units in the presence of KPF₆ could be enhanced by the supramolecular effects between the OEG linkers and the potassium metal ion. Thus, the monomer feeding concentration could be largely improved, which may benefit preparation of the cyclopolymers with high degrees of copolymerization. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 330–338     

Cyclodextrins in Polymer Synthesis: Photoinitiated Free‐Radical Polymerization of N‐Isopropylacrylamide in Water Initiated by a Methylated β‐Cyclodextrin/2‐Hydroxy‐2‐methyl‐1‐phenylpropan‐1‐one Host/Guest Complex

Methylated β‐cyclodextrin (Me‐β‐CD) was used to complex a free‐radical photoinitiator, 2‐hydroxy‐2‐methyl‐1‐phenylpropan‐1‐one ( 1 ), yielding the water‐soluble 1 : 1 host/guest complex 1 a . The structure of complex 1 a was verified by means of IR, UV/vis and ¹H NMR spectroscopy. The influence of Me‐β‐CD as the host on the photopolymerization kinetics of N‐isopropylacrylamide was studied. Compared to the photopolymerization carried out under nearly identical conditions but without cyclodextrin, an increase in the polymerization rate was registered in the presence of complex 1 a .     

Dendronized tricyanopyrroline‐based chromophores in nonlinear optical active host polymer

We synthesized new nonlinear optical (NLO) chromophores containing a 3,5‐bis(3,5‐bisbenzyloxy‐benzyloxy)‐benzoate dendron. Tricyanopyrroline (TCP)‐based chromophores were designed and prepared by virtue of its strong electron withdrawing property. A soluble polyimide containing 6‐({4‐[2‐(1‐allyl‐4‐cyano‐5‐dicyanomethylene‐2‐oxo‐2,5‐dihydro‐1H‐pyrrol‐3‐yl)‐vinyl]‐phenyl}‐butyl‐amino)‐hexanoyl group in the side chain was also prepared as an NLO active host polymer. A benzoate dendron was tethered at two different binding positions of the chromophore to yield two different guest molecules. Thin‐film composites of these dendronized chromophores dissolved in the NLO active polyimide host were employed to fabricate the electro‐optic (EO) samples. The EO properties of new NLO polyimides containing dendronized chromophores were compared with those of the sample with nondendronized plain chromophores. The effect of a bulky dendron on the EO properties was investigated using an in situ reflection technique. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 5064–5076, 2008     

Synthesis of graft copolymers with “V‐shaped” and “Y‐shaped” side chains via controlled radical and anionic polymerizations

A combination of nitroxide‐mediated radical polymerization and living anionic polymerization was used to synthesize a series of well‐defined graft (co)polymers with “V‐shaped” and “Y‐shaped” branches. The polymer main chain is a copolymer of styrene and p‐chloromethylstyrene (PS‐co‐PCMS) prepared via nitroxide‐mediated radical polymerization. The V‐shaped branches were prepared through coupling reaction of polystyrene macromonomer, carrying 1,1‐diphenylethylene terminus, with polystyryllithium or polyisoprenyllithium. The Y‐shaped branches were prepared throughfurther polymerization initiated by the V‐shaped anions. The obtained branches, carrying a living anion at the middle (V‐shaped) or at the end of the third segment (Y‐shaped), were coupled in situ with pendent benzyl chloride of PS‐co‐PCMS to form the target graft (co)polymers. The purified graft (co)polymers were analyzed by size exclusion chromatography equipped with a multiangle light scattering detector and a viscometer. The result shows that the viscosities and radii of gyration of the branched polymers are remarkably smaller than those of linear polystyrene. In addition, V‐shaped product adopts a more compact conformation in dilute solution than the Y‐shaped analogy. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 4013–4025, 2007     

Atom transfer radical polymerization of hexyl acrylate and preparation of its “all‐acrylate” block copolymers

This investigation reports the polymerization of hexyl acrylate (HA) using atom transfer radical polymerization technique and subsequently the preparation of its di‐ and triblock copolymers with methyl methacrylate. Atom transfer radical polymerization of HA was investigated using different initiators and CuBr or CuCl as catalyst in combination with varying ligands, e.g., 2,2′‐bipyridine and N,N,N′,N″,N″‐pentamethyl diethylenetriamine. Reaction parameters were adjusted to successfully polymerize HA with well‐defined molecular weights and narrow polydispersity indices. The polymerization was better controlled by the addition of polar solvents, which created a homogeneous catalytic system. UV–vis analysis showed that the polar solvent, acetone coordinated with copper (I), changes the nature of the copper catalyst, thereby influencing the dynamic equilibrium of activation–deactivation cycle. This resulted in improved control over polymerization as well as in lowering the polydispersity indices, but at the cost of polymerization rate compared with the bulk process. The presence of ? Br end group in the polymer chains was confirmed by ¹H NMR as well as MALDI‐TOF mass analysis. In addition, poly(hexyl acrylate) was used as macroinitiator to prepare various “all‐acrylate” block (diblock, triblock) copolymers that were characterized by GPC and ¹H NMR. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 3499–3511, 2008     

1,5‐Diphenyl‐1,4‐diyn‐3‐one: A highly efficient photoinitiator

In a continuation of our research on new chromophores for photoinitiators (PIs), we investigated a triple‐bond‐containing benzophenone derivative. 1,5‐Diphenyl‐1,4‐pentadiyn‐3‐one ( 2 ) was prepared from phenylacetylene and ethyl formate by a one‐pot reaction. Differential scanning photocalorimetry experiments in lauryl acrylate of 2 showed surprisingly high activity for the double‐bond conversion and rate of polymerization at the lowest PI concentrations and even without any coinitiator. By the application of monomers with abstractable hydrogens, significant improvement in the photoreactivity was observed. Ultraviolet–visible spectroscopy revealed strong absorption up to 350 nm. Steady‐state photolysis experiments proved that the photochemistry of this compound was faster than that of benzophenone. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 101–111, 2005     

Use of β‐cyclodextrins to control the structure of water‐soluble copolymers with hydrophobic parts

In this article, we present the synthesis and characterization of water‐soluble polymers with hydrophobic moieties. The polymers were synthesized in aqueous solutions utilizing β‐cyclodextrins as solubility enhancers to bring the hydrophobic monomers into solution. Polymers were made with different spacing between polymer backbone and phenyl moiety by using styrene, allylbenzene, and 4‐phenyl‐1‐butene as hydrophobic moieties, respectively. The effect of the presence of CDs during synthesis as well as this difference in spacing was investigated by rebinding free β‐CDs to the polymers. The interactions between polymers and CDs were studied by ITC and this revealed some differences between the polymers. Polymers made in the presence of CDs showed a markedly stronger binding to free CDs. The same was observed with polymers with a longer spacing between backbone and phenyl moiety. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 6619–6629, 2009     

ABC‐type hetero‐arm star terpolymers through “Click” chemistry

Hetero‐arm star ABC‐type terpolymers, poly(methyl methacrylate)‐polystyrene‐poly(tert‐butyl acrylate) (PMMA‐PS‐PtBA) and PMMA‐PS‐poly(ethylene glycol) (PEG), were prepared by using “Click” chemistry strategy. For this, first, PMMA‐b‐PS with alkyne functional group at the junction point was obtained from successive atom transfer radical polymerization (ATRP) and nitroxide‐mediated radical polymerization (NMP) routes. Furthermore, PtBA obtained from ATRP of tBA and commercially available monohydroxyl PEG were efficiently converted to the azide end‐functionalized polymers. As a second step, the alkyne and azide functional polymers were reacted to give the hetero‐arm star polymers in the presence of CuBr/N,N,N′,N″,N″‐pentamethyldiethylenetriamine ( PMDETA) in DMF at room temperature for 24 h. The hetero‐arm star polymers were characterized by ¹H NMR, GPC, and DSC. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 5699–5707, 2006     

Synthesis of D‐π‐A‐π type benzodithiophene‐quinoxaline copolymers by direct arylation and their application in organic solar cells

Conjugated copolymers based on benzodithiophene (BDT) derivatives and thiophene‐quinoxaline‐thiophene (TQT) segments represent an efficient class of light harvesting materials for organic photovoltaic (OPV) applications. Commonly, BDT‐TQT copolymers are synthesized by Stille cross‐coupling polymerization. In this study, alkoxy and thienyl functionalized alternating BDT‐alt‐TQT copolymers are synthesized by direct arylation polymerization (DArP), using Ozawa conditions. An extensive optimization of the reaction conditions such as the catalytic system, solvent, temperature, base, and the concentration of the catalyst is accomplished. The optical and electrochemical properties of the copolymers obtained by DArP are compared to the reference polymers synthesized by Stille cross‐coupling polymerization. Finally, the optimized BDT‐alt‐TQT copolymers are incorporated into organic solar cells as electron donors. The solar cells of the DArP copolymers exhibit power conversion efficiencies up to 80% (rel.) of their Stille cross coupling analogues. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2018 , 56, 1457–1467     

Preparation of comb‐like copolymers with amphiphilic poly(ethylene oxide)‐b‐polystyrene graft chains by combination of “graft from” and “graft onto” strategies

A novel method for preparation the comb‐like copolymers with amphihilic poly(ethylene oxide)‐block‐poly(styrene) (PEO‐b‐PS) graft chains by “graft from” and “graft onto” strategies were reported. The ring‐opening copolymerization of ethylene oxide (EO) and ethoxyethyl glycidyl ether (EEGE) was carried out first using α‐methoxyl‐ω‐hydroxyl‐poly(ethylene oxide) (mPEO) and diphenylmethyl potassium (DPMK) as coinitiation system, then the EEGE units on resulting linear copolymer mPEO‐b‐Poly(EO‐co‐EEGE) were hydrolyzed and the recovered hydroxyl groups were reacted with 2‐bromoisobutyryl bromide. The obtained macroinitiator mPEO‐b‐Poly(EO‐co‐BiBGE) can initiate the polymerization of styrene by ATRP via the “Graft from” strategy, and the comb‐like copolymers mPEO‐b‐[Poly(EO‐co‐Gly)‐g‐PS] were obtained. Afterwards, the TEMPO‐PEO was prepared by ring‐opening polymerization (ROP) of EO initiated by 4‐hydroxyl‐2,2,6,6‐tetramethyl piperdinyl‐oxy (HTEMPO) and DPMK, and then coupled with mPEO‐b‐[Poly(EO‐co‐Gly)‐g‐PS] by atom transfer nitroxide radical coupling reaction in the presence of cuprous bromide (CuBr)/N,N,N′,N″,N″‐pentamethyldiethylenetriamine (PMDETA) via “Graft onto” method. The comb‐like block copolymers mPEO‐b‐[Poly(EO‐co‐Gly)‐g‐(PS‐b‐PEO)] were obtained with high efficiency (≥90%). The final product and intermediates were characterized in detail. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 1930–1938, 2009     

Reactions of Me2Si(2‐Me‐4,5‐BenzInd)Zr(Cl)(NEt2) and Me2Si(2‐Me‐4,5‐BenzInd)ZrCl2 (BenzInd = benzindenyl) with trimethylaluminum and methylaluminumoxane: Correlation of spectroscopy and propene polymerizations

The activity of metallocene/methylaluminumoxane (MAO) catalysts in olefin polymerization is highly dependent on both the alkylation and activation of the complexes. The leaving ligands have an important role in the complex activation, influencing the activity of the system. The aim of this work was to study the reactions of complexes Me₂Si(2‐Me‐4,5‐BenzInd)₂ZrCl₂ ( A ; BenzInd = benzindenyl) and Me₂Si(2‐Me‐4,5‐BenzInd)₂Zr(Cl)(NEt₂) ( B ) with trimethylaluminum (TMA) and MAO. The reaction kinetics and products were studied by both ultraviolet–visible and NMR spectroscopy. In addition, the polymerization behavior of the different species was investigated in propene polymerizations. Complex B was more easily monomethylated by TMA than complex A and resulted in L₂Zr(Me)(NR₂)‐type species. Monomethylation of the complexes before polymerization enhanced the polymerization activity of both complexes. When complexes A and B reacted with MAO, similar cationic species were formed, giving equal polymerization activities. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 6455–6464, 2005     

Copper(0)‐mediated living radical polymerization of acrylonitrile: SET‐LRP or AGET‐ATRP

Cu(0)‐mediated living radical polymerization was first extended to acrylonitrile (AN) to synthesize polyacrylonitrile with a high molecular weight and a low polydispersity index. This was achieved by using Cu(0)/hexamethylated tris(2‐aminoethyl)amine (Me₆‐TREN) as the catalyst, 2‐bromopropionitrile as the initiator, and dimethyl sulfoxide (DMSO) as the solvent. The reaction was performed under mild reaction conditions at ambient temperature and thus biradical termination reaction was low. The rapid and extensive disproportionation of Cu(I)Br/Me₆‐TREN in DMSO/AN supports a mechanism consistent with a single electron transfer‐living radical polymerization (SET‐LRP) rather than activators generated by electron transfer atom transfer radical polymerization (AGET ATRP). ¹H NMR analysis and chain extension experiment confirm the high chain‐end functionality of the resultant polymer. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010     

Integration of CuAAC Polymerization and Controlled Radical Polymerization into Electron Transfer Mediated “Click‐Radical” Concurrent Polymerization

The successful chain‐growth copper(I)‐catalyzed azide–alkyne cycloaddition (CuAAC) polymerization employing Cu(0)/pentamethyldiethylenetriamine (PMDETA) and alkyl halide as catalyst is first investigated by a combination of nuclear magnetic resonance, gel‐permeation chromatography, and matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry. In addition, the electron transfer mediated “click‐radical” concurrent polymerization utilizing Cu(0)/PMDETA as catalyst is successfully employed to generate well‐defined copolymers, where controlled CuAAC polymerization of clickable ester monomer is progressed in the main chain acting as the polymer backbone, the controlled radical polymerization (CRP) of acrylic monomer is carried out in the side chain. Furthermore, it is found that there is strong collaborative effect and compatibility between CRP and CuAAC polymerization to improve the controllability.

     

Coordination of nickel and copper dithiolate to 2,2′‐bipyridine‐based π‐conjugated polymers

π‐Conjugated polymers (Poly1–Poly3) containing a 2,2′‐bipyridine (bpy) unit were subjected to coordination to nickel and copper dithiolate for the purpose of manipulating the photophysical properties. The absorption maximum peak of Poly1 [maximum wavelength (λ_max) = 446 nm] redshifted by 36 nm upon the coordination of bpy to NiCl₂, which produced Poly1–NiCl₂. A further bathochromic shift was observed in the spectrum of Poly1–mntNi [mntNi = (maleonitrile dithiolate)nickel; λ_max = 499 nm] bearing the dithiolate ligand, which stemmed from the extension of the conjugated system over the nickel dithiolate moiety through the bpy unit. An increase in the [Ni]/[bpy] ratio in Poly1–mntNi rendered the original maximum peak at 446 nm smaller and the lower energy charge‐transfer peak at 499 nm larger; the isosbestic points remained at 380 and 475 nm. The green fluorescence (λ_max = 504 nm) emitted from Poly1 markedly diminished upon the coordination of nickel dithiolate because of the effective energy transfer. The absorption maximum peak of Poly1–mntNi in chloroform at 499 nm blueshifted to 471 nm when the volume ratio of the chloroform/N,N‐dimethylformamide solvent reached 10:90. The coordination of nickel dithiolate to Poly2 and Poly3 also brought about redshifts of the absorption maximum peaks of as much as 55 and 61 nm, respectively. The absorption maximum peak of Poly1–(phenyldithiolate)nickel(pdtNi) (λ_max = 474 nm) redshifted by 28 nm in comparison with that of Poly1, whereas the magnitude of the shift of Poly1–bis(thiophenoxide)nickel(btpNi) bearing two thiophenoxide ligands was 20 nm. Poly1–mntCu with a tetrahedral copper center was also investigated. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 2631–2639, 2004     

Synthesis of meso‐Pyrrole‐Substituted 22‐Oxacorroles by a “3+2” Approach

Unsymmetrical 22‐oxacorrole containing two aryl groups and one pyrrole group at the meso position was synthesized by condensing one equivalent of 16‐oxatripyrrane with one equivalent of meso aryl dipyromethane under mild acid‐catalyzed conditions followed by oxidation with 2,3‐dichloro‐5,6‐dicyano‐1,4‐benzoquinone (DDQ). This [3+2] condensation approach was expected to yield meso‐free 25‐oxasmaragdyrin but unexpectedly afforded unsymmetrical meso‐pyrrole‐substituted 22‐oxacorrole. We demonstrated the versatility of the reaction by synthesizing four new meso‐pyrrole‐substituted 22‐oxacorroles. The reactivity of α‐position of meso‐pyrrole was tested by carrying out various functionalization reactions such as bromination, formylation, and nitration and obtained the functionalized meso‐pyrrole‐substituted 22‐oxacorroles in decent yields. The X‐ray structure obtained for one of the functionalized meso‐pyrrole substituted 22‐oxacorrole revealed that the macrocycle was nearly planar and the meso‐pyrrole was in the perpendicular orientation with respect to the macrocyclic plane. The meso‐pyrrole‐substituted 22‐oxacorroles absorb strongly in 400–700 nm region with one strong Soret band and four weak Q bands. The 22‐oxacorroles are strongly fluorescent and showed emission maxima at ≈650 nm with decent quantum yields and singlet‐state lifetimes. The 22‐oxacorroles are redox‐active and exhibited three irreversible oxidations and one or two reversible reduction(s). A preliminary biological study indicated that meso‐pyrrole corroles are biocompatible.     

Synthesis,purification, and characterization of “perfect” star polymers via “Click” coupling

The copper (I)‐catalyzed azide‐alkyne cycloaddition “click” reaction was successfully applied to prepare well‐defined 3, 6, and 12‐arms polystyrene and polyethylene glycol stars. This study focused particularly on making “perfect” star polymers with an exact number of arms, as well as developing techniques for their purification. Various methods of characterization confirmed the star polymers high purity, and the structural uniformity of the generated star polymers. In particular, matrix‐assisted laser desorption ionization‐time‐of‐flight mass spectrometry revealed the quantitative transformation of the end groups on the linear polymer precursors and confirmed their quantitative coupling to the dendritic cores to yield star polymers with an exact number of arms. In addition to preparing well‐defined polystyrene and poly(ethylene glycol)homopolymer stars, this technique was also successfully applied to amphiphilic, PCL‐b‐PEG star polymers. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

A Constrained Disorder Refinement: “Reinvestigation of “Single‐Crystal X‐ray Structure of 1,3‐Dimethylcyclobutadiene” by M. Shatruk and I. V. Alabugin”

Shatruk and Alabugin propose an alternative structural model for the observed electron density that we have attributed to the photochemical formation of 1,3‐dimethylcyclobutadiene in a protective solid crystalline matrix. The main criticism from Shatruk and Alabugin concerns the modeling of the disorder in the calixarene cavity and in particular the neglect of a residual electron density close to the O1 atom. We published (Chem. Eur. J. 2011 , 17, 10021) our opinion concerning this “ignored peak” in the Supporting Information of the paper. The current response to the Correspondence demonstrates that Shatruk and Alabugin have over‐modeled our data by assigning a small electron density peak, which is hardly more than the density corresponding to a hydrogen atom, to an under‐occupied oxygen site, using inappropriate refinement contraints.