Synthesis,Bifunctionalization, and Remarkable Adsorption Performance of Benzene‐Bridged Periodic Mesoporous Organosilicas Functionalized with High Loadings of Carboxylic Acids

Highly ordered benzene‐bridged periodic mesoporous organosilicas (PMOs) that were functionalized with exceptionally high loadings of carboxylic acid groups (COOH), up to 80 mol % based on silica, have been synthesized and their use as adsorbents for the adsorption of methylene blue (MB), a basic dye pollutant, and for the loading and release of doxorubicin (DOX), an anticancer drug, is demonstrated. These COOH‐functionalized benzene? silicas were synthesized by the co‐condensation of 1,4‐bis(triethoxysilyl) benzene (BTEB) and carboxyethylsilanetriol sodium salt (CES), an organosilane that contained a carboxylic acid group, in the presence of non‐ionic oligomeric surfactant Brij 76 in acidic medium. The materials thus obtained were characterized by a variety of techniques, including powder X‐ray diffraction (XRD), nitrogen‐adsorption/desorption isotherms, TEM, and ¹³C and ²⁹Si solid‐state NMR spectroscopy. Owing to the exceptionally high loadings of COOH groups, their high surface areas, and possible π? π‐stacking interactions, these adsorbents have very high adsorption capacities and extremely rapid adsorption rates for MB removal and for the controlled loading/release of DOX, thus manifesting their great potential for environmental and biomedical applications.     

Ethane‐Bridged Periodic Mesoporous Organosilicas Functionalized with High Loadings of Carboxylic Acid Groups: Synthesis,Bifunctionalization, and Fabrication of Metal Nanoparticles

Well‐ordered periodic mesoporous organosilicas (PMOs) functionalized with high contents of carboxylic acid (?COOH) groups, up to 85 mol % based on silica, were synthesized by co‐condensation of 1,2‐bis(triethoxysilyl)ethane (BTEE) and carboxyethylsilanetriol sodium salt (CES) under acidic conditions by using alkyl poly(oxyethylene) surfactant Brij 76 as a structure‐directing agent. A variety of techniques including powder X‐ray diffraction (XRD), nitrogen adsorption/desorption, Fourier‐transformed infrared (FTIR), transmission electron microscopy (TEM), ¹³C‐ and ²⁹Si solid‐state nuclear magnetic resonance (NMR) were used to characterize the products. The materials thus obtained were used as an effective support to synthesize metal nanoparticles (Ag and Pt) within the channel of 2D hexagonal mesostructure of PMOs. The size and distribution of the nanoparticles were observed to be highly dependent on the interaction between the carboxylic acid functionalized group and the metal precursors. The size of Pt nanoparticles reduced from 3.6 to 2.5 nm and that of Ag nanoparticles reduced from 5.3 to 3.4 nm with the increase in the ?COOH loading from 10 to 50 %.     

Clickable Periodic Mesoporous Organosilicas: Synthesis,Click Reactions,and Adsorption of Antibiotics

Pharmaceutical antibiotics are not easily removed from water by conventional water‐treatment technologies and have been recognized as new emerging pollutants. Herein, we report the synthesis of clickable azido periodic mesoporous organosilicas (PMOs) and their use as adsorbents for the adsorption of antibiotics. Ethane‐bridged PMOs, functionalized with azido groups at different densities, were synthesized by the co‐condensation of 1,2‐bis(trimethoxysilyl)ethane (BTME) and 3‐azidopropyltrimethoxysilane (AzPTMS), in the presence of nonionic‐surfactant triblock‐copolymer P123, in an acidic medium. Four different alkynes were conjugated to azide‐terminated PMOs by means of an efficient click reaction. The clicked PMOs showed improved adsorption capacity (241 μg g^?1) for antibiotics (ciprofloxacin hydrochloride) compared with azido‐functionalized PMOs because of the enhanced π–π stacking interactions. These results indicate that click reactions can introduce multifunctional groups onto PMOs, thus demonstrating the great potential of PMOs for environmental applications.     

Periodic mesoporous silica‐supported Ni(II) organometallic complex as an active and reusable nanocatalyst for water‐medium Sonogashira coupling reaction

Phenyl‐bridged periodic mesoporous organosilicas (PMOs) functionalized with diphenylphosphino (PPh₂‐) ligands were synthesized via a surfactant‐directed self‐assembly approach, and were used as a support to immobilize Ni(II) organometallic complex by coordination interaction. In comparison with Ni‐PPh₂‐SBA‐15 and Ni‐PPh₂‐PMOs(Et) catalysts, the as‐prepared Ni‐PPh₂‐PMOs(Ph) exhibited superior catalytic reactivity and selectivity in water‐medium Sonogashira reaction. A control experiment demonstrated that its high activity could be attributed to the high dispersion of Ni(II) active sites and ordered mesopore channels, which effectively diminished diffusion limitation. Meanwhile, the phenyl organic groups in the support wall enhanced surface hydrophobicity, which promoted the adsorption for organic reactant molecules. Moreover, it displayed almost the same catalytic efficiency with the corresponding homogeneous Ni(PPh₃)₂Cl₂ catalyst and could be used repetitively, which was considered as a more environmentally friendly catalytic process since it simultaneously avoided the use of noble metal active species and toxic organic solvents. Copyright © 2013 John Wiley & Sons, Ltd.     

Step‐Up Synthesis of Periodic Mesoporous Organosilicas with a Tyrosine Framework and Performance in Horseradish Peroxidase Immobilization

New amino‐acid‐bridged periodic mesoporous organosilicas (PMOs) were constructed by hydrolysis and condensation reactions under acid conditions in the presence of a template. The tyrosine bissilylated organic precursor (TBOS) was first prepared through a multistep reaction by using tyrosine (a natural amino acid) as the starting material. PMOs with the tyrosine framework (Tyr‐PMOs) were constructed by simultaneously using TBOS and tetraethoxysilane as complex silicon sources in the condensation process. All the Tyr‐PMOs materials were characterized by XRD, FTIR spectroscopy, N₂ adsorption–desorption, TEM, SEM, and solid‐state ²⁹Si NMR spectroscopy to confirm the structure. The horseradish peroxidase (HRP) enzyme was first immobilized on these new Tyr‐PMOs materials. Optimal conditions for enzyme adsorption included a temperature of 40 °C, a time of 8 h, and a pH value of 7. Furthermore, the novel Tyr‐PMOs materials could store HRP for approximately 40 days and maintained the enzymatic activity, and the Tyr‐PMOs–10 % HRP with the best immobilization effect could be reused at least eight times.     

Charge transport properties of triphenylamine‐pendant polypeptide

The structurally ordered polymer, triphenylamine‐pendant polypeptide (PATPA: poly[γ‐4‐(N,N‐diphenylamino‐phenyl)‐L ‐glutamine]), was prepared in order to obtain high hole mobility and high thermal stability. The hole mobility obtained for PATPA (ca. 10⁻⁵ cm²/Vsec) at room temperature is higher than that for poly(N‐vinylcarbazole) (PVK) (ca. 10⁻⁷ cm²/Vsec) or that of carbazole‐pendant polypeptide (PCLG) (ca. 10⁻⁸ cm²/Vsec). These results are supported by thermally stimulated current (TSC) measurements because the TSC can be correlated with the mobility. The glass‐transition temperature (T_g) of PATPA was estimated to be about 130° by differential scanning calorimetry (DSC). From these results, PATPA is an alternative candidate as a photoconductive polymer with high thermal stability and high hole mobility. The ordered structure along the main chain is thought to facilitate hole transport. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 38: 362–368, 2000     

Porous‐Organic‐Framework‐Templated Nitrogen‐Rich Porous Carbon as a More Proficient Electrocatalyst than Pt/C for the Electrochemical Reduction of Oxygen

Porous nitrogen‐rich carbon (POF‐C‐1000) that was synthesized by using a porous organic framework (POF) as a self‐sacrificing host template in a nanocasting process possessed a high degree of graphitization in an ordered structural arrangement with large domains and well‐ordered arrays of carbon sheets. POF‐C‐1000 exhibits favorable electrocatalytic activity for the oxygen‐reduction reaction (ORR) with a clear positive shift of about 40 mV in the onset potential compared to that of a traditional, commercially available Pt/C catalyst. In addition, irrespective of its moderate surface area (785 m² g^?1), POF‐C‐1000 showed a reasonable H₂ adsorption of 1.6 wt % (77 K) and a CO₂ uptake of 3.5 mmol g^?1 (273 K).     

Influence of Solvent‐Like Sidechains on the Adsorption of Light Hydrocarbons in Metal–Organic Frameworks

A variety of strategies have been developed to adsorb and separate light hydrocarbons in metal–organic frameworks. Here, we present a new approach in which the pores of a framework are lined with four different C3 sidechains that feature various degrees of branching and saturation. These pendant groups, which essentially mimic a low‐density solvent with restricted degrees of freedom, offer tunable control of dispersive host–guest interactions. The performance of a series of frameworks of the type Zn₂(fu‐bdc)₂(dabco) (fu‐bdc^2?=functionalized 1,4‐benzenedicarboxylate; dabco=1,4‐diazabicyclo[2.2.2]octane), which feature a pillared layer structure, were investigated for the adsorption and separation of methane, ethane, ethylene, and acetylene. The four frameworks exhibit low methane uptake, whereas C2 hydrocarbon uptake is substantially higher as a result of the enhanced interaction of these molecules with the ligand sidechains. Most significantly, the adsorption quantities and selectivity were found to depend strongly upon the type of sidechains attached to the framework scaffold.     

Ni3FeN‐Supported Fe3Pt Intermetallic Nanoalloy as a High‐Performance Bifunctional Catalyst for Metal–Air Batteries

Electrocatalysts for both the oxygen reduction and evolution reactions (ORR and OER) are vital for the performances of rechargeable metal–air batteries. Herein, we report an advanced bifunctional oxygen electrocatalyst consisting of porous metallic nickel‐iron nitride (Ni₃FeN) supporting ordered Fe₃Pt intermetallic nanoalloy. In this hybrid catalyst, the bimetallic nitride Ni₃FeN mainly contributes to the high activity for the OER while the ordered Fe₃Pt nanoalloy contributes to the excellent activity for the ORR. Robust Ni₃FeN‐supported Fe₃Pt catalysts show superior catalytic performance to the state‐of‐the‐art ORR catalyst (Pt/C) and OER catalyst (Ir/C). The Fe₃Pt/Ni₃FeN bifunctional catalyst enables Zn–air batteries to achieve a long‐term cycling performance of over 480 h at 10 mA cm⁻² with high efficiency. The extraordinarily high performance of the Fe₃Pt/Ni₃FeN bifunctional catalyst makes it a very promising air cathode in alkaline electrolyte.     

Heterogeneous Catalysis for Water Oxidation by an Iridium Complex Immobilized on Bipyridine‐Periodic Mesoporous Organosilica

Heterogenization of metal‐complex catalysts for water oxidation without loss of their catalytic activity is important for the development of devices simulating photosynthesis. In this study, efficient heterogeneous iridium complexes for water oxidation were prepared using bipyridine‐bridged periodic mesoporous organosilica (BPy‐PMO) as a solid chelating ligand. The BPy‐PMO‐based iridium catalysts (Ir‐BPy‐PMO) were prepared by postsynthetic metalation of BPy‐PMO and characterized through physicochemical analyses. The Ir‐BPy‐PMOs showed high catalytic activity for water oxidation. The turnover frequency (TOF) values for Ir‐BPy‐PMOs were one order of magnitude higher than those of conventional heterogeneous iridium catalysts. The reusability and stability of Ir‐BPy‐PMO were also examined, and detailed characterization was conducted using powder X‐ray diffraction, nitrogen adsorption, ¹³C DD MAS NMR spectroscopy, TEM, and XAFS methods.     

Well‐Defined Dinuclear Gold Complexes for Preorganization‐Induced Selective Dual Gold Catalysis

The synthesis, reactivity, and potential of well‐defined dinuclear gold complexes as precursors for dual gold catalysis are explored. Using the preorganizing abilities of the ditopic PN^HP^iPr ( L^H ) ligand, dinuclear Au^I–Au^I complex 1 and mixed‐valent Au^I–Au^III complex 2 provide access to structurally characterized chlorido‐bridged cationic species 3 and 4 upon halide abstraction. For 2 , this transformation involves unprecedented two‐electron oxidation of the redox‐active ligand, generating a highly rigidified environment for the Au₂ core. Facile reaction with phenylacetylene affords the σ,π‐activated phenylacetylide complex 5 . When applied in the dual gold heterocycloaddition of a urea‐functionalized alkyne, well‐defined precatalyst 3 provides high regioselectivities for the anti‐Markovnikov product, even at low catalyst loadings, and outperforms common mononuclear Au^I systems. This proof‐of‐concept demonstrates the benefit of preorganization of two gold centers to enforce selective non‐classical σ,π‐activation with bifunctional substrates.     

Pendant groups fine‐tuning thermal gelation of poly(ε‐caprolactone)‐b‐poly(ethylene glycol)‐b‐poly(ε‐caprolactone) aqueous solution

Novel poly(ε‐caprolactone)‐b‐poly(ethylene glycol)‐b‐poly(ε‐caprolactone) (PCL‐PEG‐PCL) bearing pendant hydrophobic γ‐(carbamic acid benzyl ester) groups (PECB) and hydrophiphilic amino groups (PECN) were synthesized based on the functionalized comonomer γ‐(carbamic acid benzyl ester)‐ε‐caprolactone (CABCL). The thermal gelation behavior of the amphiphilic copolymer aqueous solutions was examined. The phase transition behavior could be finely tuned via the pendant groups, and an abnormal phenomenon occurred that the sol–gel transition temperature shifted to a higher temperature for PECB whereas a lower temperature for PECN. The micelles percolation was adopted to clarify the hydrogel mechanism, and the effect of the pendant groups on the micellization was further investigated in detail. The results demonstrated that the introduction of γ‐(carbamic acid benzyl ester) pendant groups significantly decreased the crystallinity of the copolymer micelles whereas amino pendant groups made the micelles easy to aggregate. Thus, the thermal gelation of PEG/PCL aqueous solution could be finely tuned by the pendant groups, and the pendant groups modified PEG/PCL hydrogels are expected to have great potential biomedical application. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 2571–2581     

Enhanced Formaldehyde‐Vapor Adsorption Capacity of Polymeric Amine‐Incorporated Aminosilicas

Airborne formaldehyde, which is a highly problematic volatile organic compound (VOC) pollutant, is adsorbed by polymeric amine‐incorporated silicas (aminosilicas), and the factors that affect the adsorption performance are systematically investigated. Three different types of polymeric amines 1) poly(ethyleneimine) branched (PEIBR); 2) poly(ethyleneimine) linear (PEILI); and 3) poly(allylamine) (PAA) are impregnated into two types of porous silicas [SBA‐15 and mesocellular foam (MCF) silicas] with systematic changes of the amine loadings. The adsorption results demonstrate that the adsorption capacity increases along with the amine loading until the polymeric amines completely fill the silica pores. This results in the MCF silica, which has a larger pore volume and hence can accommodate more polymeric amine before completely filling the pore, giving materials that adsorb more formaldehyde, with the largest adsorption capacity, q, of up to 5.7 mmol_HCHO g^?1 among the samples studied herein. Of the three different types of polymers, PAA, comprised of 100 % primary amines, showed the highest amine efficiency μ (mmol_HCHO/mmol_N) for capturing formaldehyde. The chemical structures of the adsorbed formaldehyde are analyzed by ¹³C cross‐polarization magic‐angle spinning (CP‐MAS) NMR, and it is demonstrated that the adsorbed formaldehyde is chemically attached to the aminosilica surface, forming hemiaminal and imine species. Because the chemical adsorption of formaldehyde forms covalent bonds, it is not desorbed from the aminosilicas below 130 °C based on temperature‐programed‐desorption (TPD) analysis. The high formaldehyde‐adsorption capacity and stability of the trapped formaldehyde on the amine surface in this study reveal the potential utility of aminosilicas as formaldehyde abatement materials.     

Cooperative Acid–Base Effects with Functionalized Mesoporous Silica Nanoparticles: Applications in Carbon–Carbon Bond‐Formation Reactions

Acid–base bifunctional mesoporous silica nanoparticles (MSN) were prepared by a one‐step synthesis by co‐condensation of tetraethoxysilane (TEOS) and silanes possessing amino and/or sulfonic acid groups. Both the functionality and morphology of the particles can be controlled. The grafted functional groups were characterized by using solid‐state ²⁹Si and ¹³C cross‐polarization/magic angle spinning (CP/MAS) NMR spectroscopy, thermal analysis, and elemental analysis, whereas the structural and the morphological features of the materials were evaluated by using XRD and N₂ adsorption–desorption analyses, and SEM imaging. The catalytic activities of the mono‐ and bifunctional mesoporous hybrid materials were evaluated in carbon–carbon coupling reactions like the nitroaldol reaction and the one‐pot deacetalization–nitroaldol and deacetalization–aldol reactions. Among all the catalysts evaluated, the bifunctional sample containing amine and sulfonic acid groups (MSN–NNH₂–SO₃H) showed excellent catalytic activity, whereas the homogeneous catalysts were unable to initiate the reaction due to their mutual neutralization in solution. Therefore a cooperative acid–base activation is envisaged for the carbon–carbon coupling reactions.     

Construction of Pendant‐Armed Schiff‐Base Macrocyclic Dinuclear Zinc Complexes and Their Selective Recognition of Acetate Ions

Two new flexible extended dialdehydes (H₂hpdd and H₂pdd) with different functional pendant arms (? CH₂CH₂PhOH and ? CH₂CH₂Ph) have been synthesized and reacted with 1,2‐bis(2‐aminoethoxy)ethane to prepare Schiff‐base macrocyclic complexes in the presence of a Zn^II‐ion template. As a result, two preorganized dinuclear Zn^II intermediates ( 1 and 2 ), as well as two 42‐membered folded [2+2] macrocyclic dinuclear Zn^II complexes ( 3 and 4 ), were produced. The central zinc ions in compounds 1 – 4 showed distinguishable coordination patterns with the dialdehydes and the [2+2] macrocyclic ligands, in which a subtle pH‐adjustment function of the two pendant arms (with or without the phenolic hydroxy group) was believed to play a vital role. Furthermore, cation‐ and anion‐recognition experiments for complexes 3 and 4 revealed that they could selectively recognize acetate ions by the formation of 1:1 stoichiometric complexes, as verified by changes in their UV/Vis and MS (ESI) spectra and even by the naked eye.     

Electrophosphorescent Heterobimetallic Oligometallaynes and Their Applications in Solution‐Processed Organic Light‐Emitting Devices

By combining the iridium(III) ppy‐type complex (Hppy=2‐phenylpyridine) with a square‐planar platinum(II) unit, some novel phosphorescent oligometallaynes bearing dual metal centers (viz. Ir^III and Pt^II) were developed by combining trans‐[Pt(PBu₃)₂Cl₂] with metalloligands of iridium possessing bifunctional pendant acetylene groups. Photophysical and computational studies indicated that the phosphorescent excited states arising from these oligometallaynes can be ascribed to the triplet emissive Ir^III ppy‐type chromophore, owing to the obvious trait (such as the longer phosphorescent lifetime at 77 K) also conferred by the Pt^II center. So, the two different metal centers show a synergistic effect in governing the photophysical behavior of these heterometallic oligometallaynes. The inherent nature of these amorphous materials renders the fabrication of simple solution‐processed doped phosphorescent organic light‐emitting diodes (PHOLEDs) feasible by effectively blocking the close‐packing of the host molecules. Saliently, such a synergistic effect is also important in affording decent device performance for the solution‐processed PHOLEDs. A maximum brightness of 3 356 cd m^?2 (or 2 708 cd m^?2), external quantum efficiency of 0.50 % (or 0.67 %), luminance efficiency of 1.59 cd A^?1 (or 1.55 cd A^?1), and power efficiency of 0.60 Lm W^?1 (or 0.55 Lm W^?1) for the yellow (or orange) phosphorescent PHOLEDs can be obtained. These results show the great potential of these bimetallic emitters for organic light‐emitting diodes.     

Adsorptive Separation of Acetylene from Light Hydrocarbons by Mesoporous Iron Trimesate MIL‐100(Fe)

A reducible metal–organic framework (MOF), iron(III) trimesate, denoted as MIL‐100(Fe), was investigated for the separation and purification of methane/ethane/ethylene/acetylene and an acetylene/CO₂ mixtures by using sorption isotherms, breakthrough experiments, ideal adsorbed solution theory (IAST) calculations, and IR spectroscopic analysis. The MIL‐100(Fe) showed high adsorption selectivity not only for acetylene and ethylene over methane and ethane, but also for acetylene over CO₂. The separation and purification of acetylene over ethylene was also possible for MIL‐100(Fe) activated at 423 K. According to the data obtained from operando IR spectroscopy, the unsaturated Fe^III sites and surface OH groups are mainly responsible for the successful separation of the acetylene/ethylene mixture, whereas the unsaturated Fe^II sites have a detrimental effect on both separation and purification. The potential of MIL‐100(Fe) for the separation of a mixture of C₂H₂/CO₂ was also examined by using the IAST calculations and transient breakthrough simulations. Comparing the IAST selectivity calculations of C₂H₂/CO₂ for four MOFs selected from the literature, the selectivity with MIL‐100(Fe) was higher than those of CuBTC, ZJU‐60a, and PCP‐33, but lower than that of HOF‐3.     

Bismuth‐Containing SBA‐15 Mesoporous Silica Catalysts for Solvent‐Free Liquid‐Phase Oxidation of Cyclohexane by Molecular Oxygen

Bismuth (Bi)‐containing SBA‐15 mesoporous silica catalysts, Bi/SBA‐15, with different Bi loadings were synthesized by a direct hydrothermal method. The materials were characterized in detail by various techniques. Powder‐X‐ray‐diffraction (PXRD), N₂‐adsorption/desorption, and transmission‐electron‐microscopic (TEM) analyses revealed that the well‐ordered hexagonal structure of SBA‐15 is maintained after Bi incorporation. Diffuse‐reflectance UV/VIS, Raman, and X‐ray photoelectron spectroscopy (XPS) showed that the incorporated Bi‐atoms are highly dispersed, most of them entering the internal surface of SBA‐15. The new, very stable catalysts were found to be highly efficient for the oxidation of cyclohexane in a solvent‐free system, molecular oxygen (O₂) being used as oxidant.     

Fluorographdiyne: A Metal‐Free Catalyst for Applications in Water Reduction and Oxidation

A highly efficient bifunctional metal‐free catalyst was prepared by growth of three‐dimensional porous fluorographdiyne networks on carbon cloth (p‐FGDY/CC). Our experiments and density functional theory (DFT) calculations show the 3D p‐FGDY/CC network is highly active and it is a high potential metal‐free catalyst for the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER), as well as overall water splitting (OWS) under both acidic and alkaline conditions. The experimental and theoretical results show very good consistency; for example, in the HER process, p‐FGDY/CC exhibits small overpotentials of 82 and 92 mV to achieve 10 mA cm^?2 under alkaline and acidic conditions, respectively. This ensures an even higher selectivity for the adsorption/desorption of various O/H intermediate species. The essential key promotion accomplishes a bifunctional H₂O redox performance application under pH‐universal electrochemical conditions.     

Synthesis and Rh(I)‐catalyzed polymerization of 1,3‐diphenylyne–calix[4]arene compounds: Novel conjugated,calixarene‐based polymers

The synthesis of two 1,3‐bis(4‐ethynylbenzyloxy)calix[4]arenes, 5,11,17,23‐tetrakis(1,1‐dimethylethyl)‐25,27‐bis(4‐ethynylbenzyloxy)‐26,28‐dihydroxycalix[4]arene ( 1 ) and 25,27‐bis(4‐ethynylbenzyloxy)‐26,28‐dihydroxycalix[4]arene ( 2 ), was accomplished through Sonogashira coupling of appropriate calixarene derivatives. Methods for the polymerization of these bifunctional building blocks with Rh(I) as a catalyst, leading ultimately to conjugated polymers having calix[4]arene units incorporated into the main chain, were explored. Calixarenes 1 and 2 were efficiently polymerized with rhodium‐based initiators and afforded the conjugated polymers poly{5,11,17,23‐tetrakis(1,1‐dimethylethyl)‐25,27‐bis(4‐ethynylbenzyloxy)‐26,28‐dihydroxycalix[4]arene} ( poly 1 ) and poly{25,27‐bis(4‐ethynylbenzyloxy)‐26,28‐dihydroxycalix[4]arene}. Depending on the conditions, high conversions and good yields were obtained. The effects of adding cocatalysts (NHEt₂ and/or PPh₃) were studied in connection with the number‐average molecular weight and the molecular weight distribution of the resultant polymer ( poly 1 ) and tentatively correlated with the formation of low‐molecular‐weight materials. A catalytic system containing triphenylphosphine as the sole additive ([Rh(nbd)Cl]₂; [Rh]/[PPh₃] = 0.5) proved to be the best for the polymerization of p‐tert‐butylcalixarene compound 1 . Linear polymers having high number‐average molecular weights (up to 1.1 × 10⁵ g mol^?1) with low polydispersities were produced under these conditions. For debutylated homologue 2 , its polymerization was best carried out in the absence of any added cocatalyst. A cyclopolymerization route, comprising the intramolecular ring closing of the calix[4]arene pendant ethynyl groups followed by an intermolecular propagation step, is advanced to explain the results. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 7054–7070, 2006