Synthesis of Branched Polymers by Means of Living Anionic Polymerization, 9. Radical Coupling Reaction of 1,1‐Diphenylethylene‐Functionalized Polymers with Potassium Naphthalenide and Its Application to Syntheses of In‐Chain‐Functionalized Polymers and Star‐Branched Polymers

Radical coupling reactions of both 1,1‐diphenylethylene (DPE)‐chain‐end‐ and DPE‐in‐chain‐functionalized polymers with potassium naphthalenide have been studied under the conditions mainly in THF at –78°C. Chain‐end‐functionalized polymers having M̄_n values of less than 10 kg/mol were very efficiently coupled in more than 90% yield to afford the polymeric dianion that were dimeric coupled products with two 1,1‐diphenylalkyl anions in the middle of the chains. However, the dimer yield decreased with increasing the molecular weight. The dimer was obtained in 59% yield with use of the chain‐end‐functionalized polymer having M̄_n of 33.9 kg/mol. Well‐defined in‐chain‐functionalized polymers with two benzyl bromide and DPE moieties each have been successfully synthesized by the reaction of the polymeric dianion thus obtained with 1‐(4‐bromobutyl)‐4‐(tert‐butyldimethylsilyloxymethyl)benzene and 1‐[4‐(4‐bromobutyl)phenyl]‐1‐phenylethylene, respectively. The radical coupling reaction of in‐chain‐functionalized polymers with DPE (M̄_n ca. 20 kg/mol) with potassium naphthalenide also proceeded efficiently to afford the coupled products that were A₂A′₂ and A₂B₂ four‐arm star‐branched polymers with well‐defined structures (M̄_n ca. 40 kg/mol).     

Synthesis of Branched Polymers by Means of Living Anionic Polymerization, 8. Synthesis of Well‐Defined Star‐Branched Polymers by an Iterative Approach Based on Living Anionic Polymerization Using 1,1‐Diphenylethylene Derivatives

The synthesis of well‐defined four‐ and six‐arm star branched polymers in which arms differ either in molecular weight or composition has been achieved via a new iterative approach based on living anionic polymerization using 1,1‐diphenylethylene (DPE) derivatives. Each stage in the iteration involves two reactions: a living functionalization reaction of living anionic polymer with DPE derivatives and an in‐situ reaction of the resulting linked product having two anions with 1‐4‐(4‐bromobutyl)phenyl]‐1‐phenylethylene to introduce two DPE moieties into the polymer. In each living functionalization reaction, a 1.2‐fold excess or more of living anionic polymer relative to DPE moiety was employed to complete the reaction. Asymmetric A₂A′₂ and A₂A′₂A′′₂ star‐branched polystyrenes as well as A₂B₂ and A₂B₂C₂ heteroarm star‐branched polymers were synthesized by repeating the iteration synthetic sequence two and three times, respectively. Since the polymers obtained by each reaction stage were contaminated with their precursor polymers, they were isolated by SEC fractionation. Their high degrees of compositional, molecular weight and architectural homogeneity were confirmed by the analytical results of SEC, SLS, VPO, ¹H NMR and viscosity measurements.     

Successive Synthesis of Multiarmed and Multicomponent Star‐Branched Polymers by New Iterative Methodology Based on Linking Reaction between Block Copolymer In‐Chain Anion and α‐Phenylacrylate‐Functionalized Polymer

A series of multiarmed and multicomponent miktoarm (μ‐) star polymers have been successfully synthesized by developing a new iterative methodology based on a specially designed linking reaction of the block copolymer in‐chain anions, whose anions are positioned between the blocks, with α‐phenylacrylate (PA)‐functionalized polymers. The iterative methodology involves the following two reaction steps: a) introduction of two different polymer segments by the linking reaction of a block copolymer in‐chain anion with a PA‐functionalized polymer and b) regeneration of the PA reaction site. By repeating this reaction sequence, two different polymer segments are advantageously and successively introduced into the μ‐star polymer. In practice, repetition of the reaction sequence affords well‐defined 3‐arm ABC, 5‐arm ABCDE, 7‐arm ABCDEFG, and even 9‐arm ABCDEFGHI μ‐star polymers, composed of polystyrene, polystyrenes substituted with functional groups, polyisoprene, and poly(alkyl methacrylate) arms, respectively.

     

Synthesis of Miktoarm Star‐Shaped Polymers with POSS Core via a Combination of CuAAC Click Chemistry,ATRP, and ROP Techniques

Well‐defined AB‐type miktoarm star‐shaped polymers with a polyhedral oligomeric silsesquioxane (POSS) core are prepared by combination of the “core‐first” and “arm‐first” approaches using ring‐opening polymerization (ROP) and copper‐catalyzed azide–alkyne cycloaddition (CuAAC) click reactions. The clickable octakis‐azido‐hydroxyl‐POSS as the core molecule and alkyne end‐functionalized precursor polymers (methoxypoly(ethylene glycol), poly(methyl methacrylate) (PMMA), and polystyrene) are synthesized independently according to the well‐known procedures including ring‐opening reaction of octaglycidyldimethylsilyl POSS using sodium azide, etherification of poly(ethylene glycol) (PEG) monomethyl ether using propargyl bromide and sequential atom transfer radical polymerization of methyl methacrylate or styrene and following nucleophilic substitution reactions of the these polymers with sodium azide. In subsequent step, octa‐armed poly(ε‐caprolactone) star‐shaped polymer ((PCL)₈‐POSS‐(N₃)₈) containing azido functionalities in the core is synthesized via “core‐first” approach through ROP of ε‐caprolactone (ε‐CL). Finally, alkyne end‐functionalized polymers are introduced to the (PCL)₈‐POSS‐(N₃)₈ via “arm‐first” approach using the CuAAC click reaction under ambient conditions, yielding AB‐type miktoarm star‐shaped polymers. Based on ¹H NMR spectroscopy calculations, the number of PEG, PMMA, and PSt arms in (PCL)₈‐POSS‐(mPEG)₇, (PCL)₈‐POSS‐(PMMA)₅, and (PCL)₈‐POSS‐(PSt)₆ star‐shaped polymers is found as 7.1, 4.9, and 5.9, respectively.

     

Anionic Synthesis of Epoxy End‐Capped Polymers

The reaction of living anions of polystyrene (PS) or poly(methyl methacrylate) (PMMA) with epibromohydrin for the synthesis of well‐defined epoxy end‐functionalized polymers is reported. Polyanions were reacted with an excess of epibromohydrin in tetrahydrofuran (THF) at ?78 °C. The functionalities of the resulting polymers were analyzed by matrix‐assisted laser desorption ionization time‐of‐flight mass spectrometry (MALDI‐TOF MS), NMR, and size exclusion chromatography (SEC). The epoxy end groups were reacted with 1,1‐diphenyl‐ hexyllithium, and MALDI‐TOF MS and NMR before and after this chemical modification were used to determine the presence of the epoxy end groups. The presence of the epoxy end group was confirmed by anionically polymerizing ethylene oxide from these epoxy end group. The formation of a block copolymer due to the epoxy end groups was proved by SEC analysis. The combined MALDI‐TOF MS, ¹H NMR, and SEC results indicate that epoxy end‐capped PS was obtained in quantitative yield. The method was extended to the synthesis of epoxy end‐capped PMMA. With this polymer the extent of end‐functionalization was high but not quantitative, with non‐dimeric byproducts detected by MALDI‐TOF MS.

     

Synthesis and Characterization of PNIPAm Core Cross‐Linked Star Polymers and Their Functionalization with Cyclodextrin

Poly(N‐isopropylacrylamide) (PNIPAm) core cross‐linked star (CCS) polymers (s‐(PNIPAm)_n) are synthesized by arm‐first ATRP method. The related synthesis conditions are investigated and optimized. By varying cross‐linker N,N‐methylenebisacrylamide (BIS) concentration, PNIPAm CCS polymers with about 47, 86, and 211 arms are synthesized. Then, under ATRP condition, the “living” sites at the core of s‐(PNIPAm)_n reacting with a monovinyl β‐cyclodextrin (β‐CD) monomer afford β‐CD functionalized s‐(PNIPAm)_n (CDF‐SPNIPAm). The structures of the star polymers are characterized. The results indicate that in CDF‐SPNIPAm, the ratio of β‐CD units to PNIPAm arm numbers could be up to 0.6:1. The fluorescence spectra of star polymer/ANS (8‐­anilino‐1‐naphthalenesulfonic acid ammonium salt hydrate) systems prove that the β‐CD moieties of CDF‐SPNIPAm are available for including guest molecules. By using pH‐sensitive adamantyl (Ada)‐terminated poly(4‐vinylpyridine) (Ada‐P4VP) (synthesized by ATRP strategy) as a model guest macromolecule, the host–guest complexation between β‐CD units of CDF‐SPNIPAm and adamantyl groups of Ada‐P4VP is confirmed via 2D NOESY ¹H NMR and DLS measurements. The results indicate that the presence of the Ada‐P4VP arms provides temperature‐responsive star polymers with pH sensitivity. Therefore, the β‐CD‐functionalized star PNIPAm could provide host macromolecular platform for constructing novel miktoarm star polymers.

     

Synthesis of Branched Polymers by Means of Living Anionic Polymerization, 7. Synthesis of Well‐Defined Highly Branched Polymers and Graft Copolymers Having One Branch per Repeating Unit Using Poly(m‐halomethylstyrene)s as Backbone Polymers

Well‐defined poly(m‐chloromethylstyrene) and poly(m‐bromomethylstyrene) were prepared by the living anionic polymerization of m‐(tert‐butyldimethylsilyl)oxymethylstyrene and subsequent transformation reactions with BCl₃ and (CH₃)₃SiCl/LiBr. The reaction of poly(m‐chloromethylstyrene)s with 1,1‐diphenylethylene (DPE) end‐capped polystyryllithium proceeded very fast in the initial stage (76% of efficiency after 10 min) and reached quantitative reaction efficiency after 24 h at –40°C. The reaction of poly(m‐bromomethylstyrene) with DPE end‐capped polystyryllithium of molecular weight value of up to 68.8 kg/mol proceeded completely without steric hindrance of the polystyrene branch at –40°C for 168 h to afford a very high molecular weight branched polystyrene with one branch per repeating unit (M̄_w = 2.3 million). Well‐defined graft copolymers with the same architecture were also successfully synthesized by reacting poly(m‐halomethylstyrene)s with living anionic polymers of isoprene, 2‐vinylpyridine, and tert‐butyl methacrylate at –40°C for 168–336 h. The high compact structures of the branched polystyrenes synthesized here comparable to those of star‐branched polymers were confirmed by viscosity measurement performed in toluene at 35°C.     

Synthesis and morphology of ABC heteroarm star terpolymers of polystyrene,polybutadiene and poly(2‐vinylpyridine)

Three series of ABC heteroarm star terpolymers with arms of polystyrene (S), polybutadiene (B) and poly(2‐vinylpyridine) (V) were synthesized anionically using non‐homopolymerizable macromonomers functionalized with a terminal 1,1‐diphenylethylene unit. Ultrathin samples from solution cast films were stained with OsO₄, CH₃I or I₂ and studied by transmission electron microscopy (TEM). The morphologies found include dense packings of cylinders with tetragonal or distorted hexagonal order, two hexagonal morphologies with V cylinders surrounded by six B and six S cylinders, where S and V switch places depending on the polymer composition, lamellae of V and S with B cylinders in the S lamella and smooth lamellae of all components. Some polymers were also characterized by small angle X‐ray scattering (SAXS).     

Dibromomaleimide Derivative as an Efficient Polymer Coupling Agent for Building Topological Polymers

The dibromomaleimide derivative, N‐(4‐bromobutyl)‐dibromomaleimide (dBMIB), is found to be a highly efficient coupling agent to dimerize thiol‐terminated hydrophilic polymers by substituent reaction. When mono‐thiol poly(ethylene oxide) (PEO₄₅‐SH) is mixed with dBMIB in an equivalent molar feed in water, a dimer of PEO₄₅ with a maleimide unit located at the chain center, (PEO₄₅)₂MIB, is obtained quantitatively. The dBMIB is also used to dimerize thiol‐ terminated poly(N‐(2‐acryloyloxyethyl) pyrrolidone) and poly(N,N‐dimethyl acrylamide). Moreover, the butylene bromide of (PEO₄₅)₂MIB is transferred into a butylene azide, which is allowed to react with alkynyl‐terminated polystyrene to give a A₂B miktoarm star polymer via a copper‐catalyzed azide–alkyne cycloaddition coupling reaction.     

Dendritic‐Linear Hybrid Multiarm Star Polymers: A Straightforward Synthesis of Polymer as Molecular Nanoparticles

Synthesis of multiarm star polymers via “core first” method but possibly through two different chain growth fashions has been described. Two distinct styrenyl‐TEMPO‐based G3 and G4 dendritic unimolecular initiators have been used for this method. Polymerization of styrene using these core‐cum‐initiators at 125 °C varying the monomer to initiator ratio and polymerization time yields multiarm star polymers with molecular weight (M_w) in the range of 1.71 × 10⁵ to 4.75 × 10⁵ g mol^?1 and polydispersity in the range of 1.34–1.46. Hydrolysis leading to degradation of inner polyurethane core yields highly narrow dispersed—PDI 1.00 to 1.04—polystyrene chains, and the SEC‐MALLS data of these chains confirm the accurate control on predetermination in the number of arms up to 48 of star polymers. The specific refractive index increment (dn/dc) of the polymers is found to be decreased with decreasing weight fraction of core. The transmission electron microscope (TEM) and atomic force microscopy (AFM) images and hydrodynamic radius of chosen polymers confirm the two different chain growth fashions leading to the formation of star polymers as discrete nanoparticle in the case of initiator in which TEMPO is anchored and formation of peripherally low entangled short chains in the case of initiators in which TEMPO is end‐capped.

     

Synthesis of Functionalized Polymers by Means of Living Anionic Polymerization, 2. Synthesis of Well‐Defined Chain‐End and in‐Chain Functionalized Polymers with 1,3‐Butadienyl Groups

The synthesis of well‐defined functionalized polystyrenes and poly(methyl methacrylate)s with 1,3‐butadienyl groups has been described by the methodology based on the functionalization reactions of living anionic polymers of a new substituted 1,1‐diphenylethylene with a 1,3‐butadienyl group, 1‐[4‐(4‐methylene‐5‐hexenyl)phenyl]‐1‐phenylethylene ( 1 ). Both chain‐end and in‐chain functionalized polystyrenes with one or two 1,3‐butadienyl groups were synthesized by utilizing the addition reactions of living polystyrenes to 1 followed by methanol termination or treatment with appropriate electrophiles. On the other hand, chain‐end and in‐chain functionalized poly(methyl methacrylate)s with one or two 1,3‐butadienyl groups were obtained by the living anionic polymerization of methyl methacrylate with the adduct prepared from 1 and either s‐BuLi or lithium naphthalenide. The 1,3‐buadienyl groups thus introduced were quantitatively transformed into anhydride or epoxy functions without any side reactions by the (C₂H₅)₂AlCl‐catalyzed Diels‐Alder reaction or by treatment with 3‐chloroperoxybenzoic acid.     

Photocrosslinkable Star Polymers: Precursors for Model Polyelectrolyte Networks

A new synthetic route for the preparation of well‐defined model polyelectrolyte networks based on the photodimerization of monodisperse star polymers, bearing terminal anthryl groups, is presented. Poly(tert‐butyl methacrylate) (PtBMA) star precursor polymers were prepared via living anionic polymerization. 1‐(2‐anthryl)‐1‐phenylhexyllithium (APH‐Li) served as the novel initiator by which photo‐dimerizable anthryl groups were introduced. In order to vary the functionality of the stars, two different terminating agents were used: 1,3,5‐trisbromomethylbenzene (TBMB) and octa[(3‐iodopropyl)]‐silsesquioxane (T₈‐(prop‐I)₈). The length of the respective star arms was varied accordingly: 14 ⪇ P_n ⪇ 195. Subsequent cleavage of the tert‐butyl ester moieties by acidic hydrolysis gave access to photocrosslinkable, monodisperse polyelectrolyte star polymers. Fluorescence experiments indicated on aggregation of low molecular weight poly/methacrylic acid) (PMAA) stars in salt containing solutions. Upon irradiation with UV light (λ = 366 nm) photodimerization of the terminal anthryl groups was induced and thus formation of a well‐defined polyelectrolyte network was accomplished. In model experiments we demonstrated by ¹H‐NMR, UV‐VIS spectroscopy as well as GPC analysis, that linear ω‐anthryl‐functionalized precursor PtBMA polymers dimerize quantitatively, as long as a critical degree of polymerization (P_n ≈ 100) is not exceeded.     

Functionalization of TiO2 Nanoparticles with Semiconducting Polymers Containing a Photocleavable Anchor Group and Separation via Irradiation Afterward

The controlled radical polymerization (RAFT polymerization) of semiconducting polymers based on poly(4,4′‐dimethyl‐triphenylamine) is described. These polymers are afterward end‐functionalized with a photocleavable group and an anchor unit (catechol) for oxidic nanoparticles (NPs). Serving as a reference, polystyrene oligomers with the same end groups are also synthesized. Using these polymers allows functionalization of the TiO₂‐NPs, leading to an improved solubility and miscibility in organic solvents or polymer matrices. Irradiation in the UV region is used to split the photocleavable group and remove the polymer chains from the NPs, which leads to their aggregation.

     

Heterofunctionalized Multiarm Star Polymers via Sequential Thiol‐para‐Fluoro and Thiol‐Ene Double “Click” Reactions

The successful postfunctionalization of multiarm star polystyrene (PS) with pentafluorophenyl and allyl moieties at the periphery is demonstrated employing modular thiol‐para‐fluoro and photoinduced radical thiol‐ene double “click” reactions, respectively. α‐Fluoro and α‐allyl functionalized PS (α‐fluoro‐PS and α‐allyl‐PS) are in situ prepared by atom transfer radical polymerization of styrene and their mixture is used as macroinitiator in a crosslinking reaction with divinyl benzene (DVB) yielding (fluoro‐PS)_m–polyDVB–(allyl‐PS)_m multiarm star polymer. It is found that the multiarm star polymer includes nearly identical number of arms possessing pentafluorophenyl and allyl moieties at the periphery. The obtained multiarm star polymer is then reacted with 1‐propanethiol through thiol‐para‐fluoro “click” reaction to give (propyl‐PS)_m–polyDVB–(allyl‐PS)_m multiarm star polymer, which is subsequently reacted with N‐acetyl‐l ‐cysteine methyl ester via radical thiol‐ene “click” reaction in order to give well‐defined heterofunctionalized (propyl‐PS)_m–polyDVB–(cysteine‐PS)_m multiarm star polymer, with higher molecular weight and narrow molecular weight distribution. Multiarm star polymers are characterized by using viscotek triple detection gel permeation chromatography, ¹H, and ¹⁹F NMR.

     

Synthesis and Gas Permeation Properties of Spirobischromane‐Based Polymers of Intrinsic Microporosity

Polymers of intrinsic microporosity (PIMs) possess molecular structures composed of fused rings with linear units linked together by a site of contortion so that the macromolecular structure is both rigid and highly non‐linear. For PIM‐1, which has previously demonstrated encouraging gas permeability data, the site of contortion is provided by the monomer 5,5′,6,6′‐tetrahydroxy‐3,3,3′,3′‐tetramethyl‐1,1′‐spirobisindane. Here we describe the synthesis and properties of a PIM derived from the structurally related 6,6′,7,7′‐tetrahydroxy‐4,4,4′,4′‐tetramethyl‐2,2′‐spirobischromane and copolymers prepared from combination of this monomer with other PIM‐forming biscatechol monomers, including the highly rigid monomer 9,10‐dimethyl‐9,10‐ethano‐9,10‐dihydro‐2,3,6,7‐tetrahydroxyanthracene. Generally, the polymers display good solubility in organic solvents and have high average molecular masses ( ) in the range 80 000–200 000 g · mol^?1 and, therefore, are able to form robust, solvent‐cast films. Gas permeability and selectivity for He, H₂, N₂, O₂, CO₂, and CH₄ were measured for the polymers and compared to the values previously obtained for PIM‐1. The spirobischromane‐based polymers demonstrate enhanced selectivity for a number of gas pairs but with significantly lower values for permeability. The solubility coefficient for CO₂ of two of the copolymers exceed even that of PIM‐1, which previously demonstrated the highest value for a membrane‐forming polymer. Therefore, these polymers might be useful for gas or vapor separations relying on solubility selectivity.

     

Imidazolium End‐Functionalized ATRP Polymers as Directing Agents for CNT Dispersion and Confinement

Imidazolium end‐functionalized poly(butyl acrylate) and polystyrene (co)polymers (Im‐PnBuA, Im‐PSty, and Im‐PnBuA‐b‐PSty are synthesized via ATRP. The controlled character of the polymerization reactions is highlighted by SEC and MALDI‐TOF MS analyses. Subsequently, the polymers are tested as dispersing/compatibilizing agents for CNTs in polymer matrices. When CNTs are challenged with a mixture of Im‐PnBuA and Im‐PSty, the CNTs are mainly located in the PnBuA phase. In contrast, the Im‐PnBuA‐b‐PSty block copolymer enables CNT confinement in the PSty phase. By selecting the proper ω‐imidazolium polymer, it is possible to direct the CNT confinement toward a specific polymer phase within polymer mixtures.     

Terminal Group Effect of Conjugated Microporous Polymers for Photocatalytic Water‐Splitting Hydrogen Evolution

Conjugated microporous polymers (CMPs) have attracted more and more attention as active materials for photocatalytic water‐splitting hydrogen evolution, however, the correlation between terminal group and hydrogen evolution performance of CMPs is rarely studied. Herein, three triazine‐based CMPs (Ta‐CMPs) with the same polymer backbone and different terminal groups (Ta‐CMP, Ta‐CMP‐N, and Ta‐CMP‐CN) are synthesized via Suzuki–Miyaura coupling reaction using different end‐capping agents. Although the Ta‐CMPs show similar porous structure and comparable band gaps, Ta‐CMP‐CN with electron‐withdrawing terminal group exhibits the highest hydrogen evolution rate (HER) of 698 µmol g^?1 h^?1 under visible light, while Ta‐CMP‐N with electron‐donating terminal group exhibits the lowest HER of 99 µmol g^?1 h^?1. It is found that the addition of electron‐withdrawing terminal group can facilitate photoinduced charge separation, thus improving photocatalytic HER performance of the CMPs.     

β‐Cyclodextrin‐Based Star Amphiphilic Copolymers: Synthesis,Characterization, and Evaluation as Artificial Channels

14‐arm amphiphilic star copolymers are synthesized according to different strategies. First, the anionic ring polymerization of 1,2‐butylene oxide (BO) initiated by per(2‐O‐methyl‐3,6‐di‐O‐(3‐hydroxypropyl))‐β‐CD (β‐CD’OH₁₄) and catalyzed by t‐BuP₄ in DMF is investigated. Analyses by NMR and SEC show the well‐defined structure of the star β‐CD’‐PBO₁₄. To obtain a 14‐arm poly(butylene oxide‐b‐ethylene oxide) star, a Huisgen cycloaddition between an α‐methoxy‐ω‐azidopoly(ethylene oxide) and the β‐CD’‐PBO₁₄,whose end‐chains are beforehand alkyne‐functionalized, is performed. In parallel, 14‐arm star copolymers composed of butylene oxide‐b‐glycidol arms are successfully synthesized by the anionic polymerization of ethoxyethylglycidyl ether (EEGE) initiated by β‐CD’‐PBO₁₄ with t‐BuP₄. The deprotection of EEGE units is then performed to provide the polyglycidol blocks. These amphiphilic star polymers are evaluated as artificial channels in lipid bilayers. The effect of changing a PEO block by a polyglycidol block on the insertion properties of these artificial channels is discussed.     

Synthesis of new amphiphilic star polymers derived from a hyperbranched macroinitiator by the cationic ‘grafting from’ method

New amphiphilic star polymers possessing a hyperbranched core and hydrophilic graft arms have been prepared. The synthetic strategy involved esterification of the 4,4-bis(4′-hydroxyphenyl)valeric acid based hyperbranched polymer with 3-(chloromethyl)benzoyl chloride to obtain the hyperbranched macroinitiator followed by cationic ring-opening polymerization of 2-methyl-2-oxazoline to give amphiphilic polymers. Exchange of the chloride counter ion with trifluoromethanesulfonate (KCF₃SO₃ or AgCF₃SO₃) or iodide (KI) anions leads to higher polymerization rates. Phenyl 2-(chloromethyl)benzoate was used as a model initiator to study the effect of different coinitiators on the initiator efficiency. KI as a coinitiator yielded 56–86% initiator conversion whereas only 30–37% initiator conversion was achieved with KCF₃SO₃ or AgCF₃SO₃ as coinitiator after quantitative monomer consumption. Photon correlation spectroscopy (PCS) in methanol and chloroform for selected graft copolymers revealed the formation of single star molecules ranging from 22 to 50 nm in diameter.     

Synthesis,Characterization, and Ion Sensing Application of Pyrene‐Containing Chemical Probes

A novel pyrene‐functionalized thiophene compound ( Thi‐Pyr ) and pyrene‐functionalized styrene polymers ( P7–9 ) are synthesized via 1,3‐dipolar cycloaddition reaction between the azide functional groups of the precursors and 1‐ethynylpyrene. Glass transition temperature of the styrene polymers increases remarkably upon the covalent attachment of the pyrene unit through triazole linkers, whereas the thermal stabilities of the styrene polymers are not affected by the incorporation of pyrene moieties. Thi‐Pyr exhibits the characteristic pyrene monomer emission bands; on the other hand, P7–9 show the excimer emission bands of pyrene due to the excitation of ground state dimeric species. The monomer emissions of Thi‐Pyr and the excimer emissions of P7–9 are distinguishably increased by the addition of HP₂O₇^3?, Cl^?, and Br^? anions. The responses of Thi‐Pyr and P7–9 to the addition of HP₂O₇^3? are stronger than any other anions, indicating their selectivity to HP₂O₇^3? anion to some extent.