Novel block ionomers. I. Synthesis and characterization of polyisobutylene‐based block anionomers

A series of novel block anionomers consisting of polyisobutylene (PIB) and poly(methacrylic acid) (PMAA) segments were prepared and characterized. The specific targets were various molecular weight diblocks (PIB‐b‐PMAA^?), triblocks (PMAA^?‐b‐PIB‐b‐PMAA^?), and three‐arm star blocks [Φ(PIB‐b‐PMAA^?)₃] consisting of rubbery PIB blocks with a number‐average degree of polymerization of 50–1000 (number‐average molecular weight = 3000–54,000 g/mol) connected to blocks of PMAA^? anions with a number‐average degree of polymerization of 5–20. The overall strategy for the synthesis of these constructs consisted of four steps: (1) synthesis by living cationic polymerization of t‐chloro‐monotelechelic, t‐chloro‐ditelechelic, and t‐chloro‐tritelechelic PIBs; (2) site transformation to obtain PIBs fitted with termini capable of mediating the atom transfer radical polymerization (ATRP) of tert‐butyl methacrylate (tBMA); (3) ATRP of tBMA, and (4) hydrolysis of poly(tert‐butyl methacrylate) to PMAA^?. The architectures created and the synthesis steps employed are summarized. Kinetic and model experiments greatly assisted in the development of convenient synthesis methods. The microarchitectures of the various block anionomers were confirmed by spectroscopy and other techniques. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 3662–3678, 2002     

Synthesis and characterization of two novel star blocks: tCum[poly(isobutylene‐b‐norbornadiene)]3 and tCum[poly(norbornadiene‐b‐isobutylene)]3

Two structurally closely related three‐arm star blocks were synthesized and characterized: tCum(PIB‐b‐PNBD)₃ and tCum(PNBD‐b‐PIB)₃ [where tCum (tricumyl) stands for the phenyl‐1,3,5‐tris(‐2‐propyl) fragment and PIB and PNBD are polyisobutylene and polynorbornadiene, respectively]. The syntheses were accomplished in two stages: (1) the preparation of the first (or inner) block fitted with appropriate chlorine termini capable of initiating the polymerization of the second (or outer) block with TiCl₄ and (2) the mediation of the polymerization of the second block. Therefore, the synthesis of tCum(PIB‐b‐PNBD)₃ was effected with tCum(PIB‐Cl^t)₃ [where Cl^t is tert‐chlorine and number‐average molecular weight (M_n) = 102,000 g/mol] by the use of TiCl₄ and 30/70 CH₃Cl/CHCl₃ solvent mixtures at ?35 °C. PNBD homopolymer contamination formed by chain transfer was removed by selective precipitation. According to gel permeation chromatography, the M_n's of the star blocks were 107,300–109,200 g/mol. NMR spectroscopy (750 MHz) was used to determine structures and molecular weights. Differential scanning calorimetry (DSC) indicated two glass‐transition temperatures (T_g's), one each for the PIB (?65 °C) and PNBD (232 °C) phases. Thermogravimetric analysis thermograms showed 5% weight losses at 293 °C in air and at 352 °C in N₂. The synthesis of tCum(PNBD‐b‐PIB)₃ was achieved by the initiation of isobutylene polymerization with tCum(PNBD‐Cl^sec)₃ (where Cl^sec is sec‐chlorine and M_n = 2900 g/mol) by the use of TiCl₄ in CH₃Cl at ?60 °C. DSC for this star block (M_n = 14,200 g/mol) also showed two T_g's, that is, at ?67 and 228 °C for the PIB and PNBD segments, respectively. It is of interest that the Cl^sec terminus of PNBD, , readily initiated isobutylene polymerization. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 740–751, 2003     

Living carbocationic polymerization. XXX. One-pot synthesis of allyl-terminated linear and tri-arm star polyisobutylenes,and epoxy- and hydroxy-telechelics therefrom

Mono- and di-ended linear and three-arm star allyl-telechelic polyisobutylenes, PIB? A, A? PIB? A and (where A = ? CH₂? CH?CH₂) have been prepared by a rapid economical one-pot polymerization-functionalization process. The process involves the living polymerization of isobutylene (IB) by mono-, di-, or tri-functional initiating systems, specifically by allphatic and aromatic tert-ester and -ether/TiCl₄ combinations, followed by electrophilic functionalization of the living sites with allyl-trimethylsilane (ATMS). Structural characterization by ¹H-NMR spectroscopy and end group titration with m-chloroperbenzoic acid (m-CPBA) indicate quantitative end allylation even with relatively slowly initiating systems like DiOAcTMH₇/TiCl₄. Detailed kinetic analysis of the latter system indicates, unexpetedly, cationation to be rate determining. Quantitative derivatizations of the allyl termini have yielded mono-, di-, and tri-epoxy- and -hydroxy-telechelic PIBs. Strong rubbery networks have been made by curing the epoxy-telechelic PIBs with triethylene tetramine and by reacting the hydroxy-telechelic PIBs with MDI.     

Multi-arm star polyisobutylenes: 2. The effect of synthesis conditions on the structure of star PIBs

Multi-arm star polyisobutylenes (^*-(PIB)_n) have been prepared by the “arm-first” method. This synthesis was accomplished by adding various linking agents (“core builders”) such as p- and m-divinylbenzene (DVB) and p- and m-diisopropenylbenzene (DIB) to living PIB® charges and thus obtaining a crosslinked aromatic core holding together a corona of well-defined arms. The products were characterized in terms of overall arm/core composition, molecular weight, and molecular weight distribution (M̄_w/M_n). The effect of reaction conditions (time, [linking agent]/[PIB], arm molecular weight) on the kinetics of the star formation and star structure were investigated. The multi-arm star nature of ^*-(PIB)_ns was proven directly by determining the molecular weight (by light scattering) of the intact products, selectively destroying the aromatic polyDVB (or polyDIB) core (“core-destruction”), and finally determining the molecular weight of the surviving aliphatic PIB arms. The synthetic strategy, overall kinetics, and observations during the preparation of star-PIBs were discussed. Among the critical parameters that determine product structures are the rate of crossover PIB^⊕ + DVB (or DIB) → PIB-DVB^⊕ (or PIB-DIB^⊕), the concentration of the linking agent DVB (or DIB), and the molecular weight of the PIB arm. Evidence for the formation of higher order stars (“secondary”, etc.) by star-star- coupling has been presented.     

Synthesis and characterization of novel dendritic (arborescent,hyperbranched) polyisobutylene–polystyrene block copolymers

The synthesis of novel arborescent (arb; randomly branched, “tree‐like,” and often called “hyperbranched”) block copolymers comprised of rubbery polyisobutylene (PIB) and glassy polystyrene (PSt) blocks (arb‐PIB‐b‐PSt) is described. The syntheses were accomplished by the use of arb‐PIB macroinitiators (prepared by the use of 4‐(2‐methoxyisopropyl) styrene inimer) in conjunction with titanium tetrachloride (TiCl₄). The effect of reaction conditions on blocking of St from arb‐PIB was investigated. Purified block copolymers were characterized by ¹H NMR spectroscopy and Size Exclusion Chromatography (SEC). arb‐PIB‐b‐PSt with 11.7–33.8 wt % PSt and M_n = 468,800–652,900 g/mol displayed thermoplastic elastomeric properties with 3.6–8.7 MPa tensile strength and 950–1830% elongation. Samples with 26.8–33.8 wt % PSt were further characterized by Atomic Force Microscopy (AFM), which showed phase‐separated mixed spherical/cylindrical/lamellar PSt phases irregularly distributed within the continuous PIB phase. Dynamic Mechanical Thermal Analysis (DMTA) and solvent swelling of arb‐PIB‐b‐PSt revealed unique characteristics, in comparison with a semicommercial PSt‐b‐PIB‐b‐PSt block copolymer. The number of aromatic branching points of the arb‐PIB macroinitiator, determined by selective destruction of the linking sites, agreed well with that calculated from equilibrium swelling data of arb‐PIB‐b‐PSt. This method for the quantitative determination of branching sites might be generally applicable for arborescent polymers. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 1811–1826, 2005     

Cationic polymerization by aromatic initiating systems. IV. Synthesis and characterization of α-ω-diphenylpolyisobutylene

The polymerization of isobutylene using ø₃Al coinitiator and the tertiary chlorides tert.-butyl chloride (t-BuCl) and 2,6-dichloro-2,6-dimethylheptane (Cl^t-R-Cl^t) initiators has been studied. Polymerization rates with the t-BuCl/ø₃Al and Cl^t-R-Cl^t/ø₃Al initiating systems were high in the ?20 to ?70°C range. Yields and molecular weights increased with decreasing temperature. As predicted by model experiments the extent of phenylation increases with decreasing temperatures. According to spectroscopic evidence the polyisobutylenes carry phenyl end groups.     

Synthetic approaches towards new polymer systems by the combination of living carbocationic and anionic polymerizations

This study summarizes recent efforts to obtain by combination of living carbocationic and anionic polymerizations block copolymers which are potential precursors for building new well-defined polymeric architectures with microphase separated morphology. Living carbocationic polymerization (LCCP) yields telechelic polyisobutylene (PIB) chains with a variety of useful endgroups, such as tert-chlorine, isopropenyl, primary hydroxyl, tolyl etc. When tolyl-ended PIB was used as precursor for macroinitiator of living anionic polymerization of 2-(tert-butyldimethylsilyloxy)ethyl methacrylate (tBuMe₂SiOEMA), mixtures of homopolymers and block copolymers were formed due to incomplete lithiation of this chain end. In another approach a new functionalization method was developed by end-quenching living PIB chains with 1,1-diphenylethylene (DPE). In the presence of BCl₃ a new telechelic PIB with 2,2-diphenylvinyl (DPV) endgroups was formed. A corresponding DPV model compound was synthesized from 2-chloro-2,4,4-trimethylpentane (TMPCl). Because of steric hindrance less than quantitative lithiation of this material occurred. Controlled deprotection of PtBuMe₂SiOEMA obtained by living anionic polymerization (LAP) was utilized to prepare a precursor network composed of partially deprotected PtBuM₂SiOEMA and hydroxyl-telechelic PIB by using a diisocyanate crosslinker. After network formation deprotection with HCl was completed and a new amphiphilic network (APN) containing PIB and poly(2-hydroxyethyl) methacrylate) (PHEMA) segments crosslinked by urethane linkages was obtained.     

Beiträge zur Chemie des Phosphors. 87. 1,2-Di-tert-butyl-3-iso-propyl-cyclotriphosphan,ein stabiles gemischt-substituiertes Cyclotriphosphan

Contributions to the Chemistry of Phosphorus. 87. 1,2-Di-tert-butyl-3-iso-propyl-cylclotriphosphane, a Stable Mixed-substituted Cyclotriphosphane The first kinetically stable mixed-substituted cyclotriphosphane, 1,2-di-tert-butyl-3-iso-propyl-cyclotriphosphane, (PBu^t)₂(PPrⁱ) ( 1 ), was synthesized by [2+1]-cyclocondensation of K(Bu^t)P–P(Bu^t)K with PrⁱPCl₂ in n-pentane. Mainly (PBu^t)₄ as well as mixed-substituted cyclotetra- and cyclopentaphosphanes are formed as by-products. 1 could be isolated in a pure state by high vacuum distillation and was thoroughly characterized. It forms two diastereomers, the more stable of which with a cis-standing tert-butyl and iso-propyl group can be stored without decomposition under inert conditions at room temperature for several days. Through thermolysis of 1 beside other alkylcyclophosphanes the mixed-substituted cyclotetraphosphanes (PBu^t)₂(PPrⁱ)₂ ( 2 ) and (PBu^t)₃(PPrⁱ) ( 3 ) are formed and their ³¹P NMR parameters are reported.     

New telechelic polymers and sequential copolymers by polyfunctional initiator-transfer agents (inifers) LVII. Chlorine telechelic poly(p-chlorostyrene)

The polymerization of p-chlorostyrene (pClSt) under carbocationic conditions has been investigated. The use of binifers 1,4-di(2-chloro-2-propyl) benzene (pDCC) and 1,3-di(2-chloro-2-propyl)-5-tert-butylbenzene (m-tBuDCC) in conjunction with BCl₃ coinitiator in CH₃Cl diluent at ?60 and ?35°C give α,ω-di-benzylic chlorine-capped polymer ^sCl? PpClSt? Cl^s. According to kinetic investigations the inifer mechanism is operative and both binifers are efficient in controlling the end structures, molecular weights, and to a certain extent molecular weight distributions (MWD). Strong circumstantial evidences have been generated to demonstrate the satisfactory synthesis of ^sCl? PpClSt? Cl^s and the absence of indanyl end-groups, i.e., structural considerations, linearity of inifer plots, quantitative Cl end-group microanalysis, FTIR spectroscopy, and blocking experiments. The latter involved the blocking of THF from the sec-benzylic chlorine end-groups by AgPF₆ and thus led to the synthesis of a new triblock copolymer PTHF-b-PpClSt-b-PTHF. Interestingly, the isotactic content (mm triads and mmmm pentads) of PpClSt is significantly higher than that of polymer prepared by free-radical induced polymerization. The T_g of a PpClSt of M?_n = 5700 g/mol was 123°C.     

Thermally reversible polymer systems by cyclopentadienylation. I. A model for termination by cyclopentadienylation of olefin polymerization

The reaction between tert-butylchloride (t-BuCl) and dimethylcyclopentadienylaluminum (Me₂AlCPD) was studied as a model for initiation by the tert-butyl cation (t-Bu^⊕) and termination by cyclopentadienylation by the Me₂Al(CPD)Cl^? counteranion of isobutylene polymerization. All reaction products formed in this model system have been identified and quantitatively determined. A comprehensive scheme that indicates pathways to these products was developed (scheme III). It is proposed that the predominant product, tert-butylcyclopentadiene (t-BuCPD), arises in the collapse of the t-Bu^⊕-Me₂Al(CPD)Cl^? ion pair, mainly by CPD^? transfer to the tert-butyl cation. The minor products are neopentane (t-BuMe) and isobutylene (i-C₄H₈), which are probably formed, respectively, by Me^? transfer to and proton loss from the t-butyl cation. Cyclopentadienylation selectivity increases by lowering the temperature and extrapolation of results suggests 100% cyclopentadienylation at ?55°C. The t-BuCl/Me₂AlCPD ratio strongly influences the overall reaction pathway. The reaction is first order in t-BuCl with ΔE_a of ca. 7 kcal/mole (1,2-dichloroethane or chlorobenzene solvents, +24 to ?29°C). Indirect evidence indicates that the kinetic product of cyclopentadienylation is 5-t-BuCPD and that this isomer cannot be tert-butylated; that is, the initiation of 5-t-BuCPD polymerization by t-Bu^⊕ is sterically unfavorable. Detailed analysis of the chemistry and kinetics of the t-BuCl/Me₂AlCPD model system holds important clues to the controlled polymerization of olefins leading to macromolecules with cyclopentadiene (CPD) termini.     

Star–block polymers of multiple polystyrene-b-polyisobutylene arms radiating from a polydivinylbenzene core

The synthesis together with mechanical property and rheological characterization of novel star–block copolymers comprising multiple polystyrene (PSt)-b-polyisobutylene (PIB) arms emanating from polydivinylbenzene (PDVB) cores are described. The synthesis strategy involved the preparation of PSt-b-PIB-Cl^t (i.e., diblocks fitted with a tert-chlorine terminus at the PIB end) by sequential living block polymerization of St and IB, ionizing the -Cl^t terminus by TiCl₄ at room temperature, and linking the PSt-b-PIB^⊕ prearms by DVB. Molecular characterization was effected mainly by triple detector GPC including refractive index (RI)-, UV-, and laser light scattering (LLS)-GPC traces. Evidence for intra- and intermolecular reactions between individual star–blocks is presented and a comprehensive mechanism to the final product is proposed. The stress–strain behavior of star–blocks has been studied and is compared with those of linear triblocks (i.e., two-arm stars) of similar arm molecular weights and composition in the 25–70°C range. The mechanical properties of star–blocks are invariably superior to those of the triblocks over the entire temperature range. The rheological behavior of star–blocks and linear triblocks has been compared in terms of dynamic viscosity at various frequencies. Star–blocks exhibit significantly lower melt viscosities than their linear counterparts, which signals improved processing behavior. We have also compared select rheological properties of the commercially available PSt-b-(hydrogenated-1,4-polybutadiene)-b-PSt thermoplastic elastomer (Kraton G 1650) with those of PIB-based linear triblocks and multiarm star–blocks of similar glassy/rubbery compositions. The melt viscosities of PIB-based triblocks and star–blocks were significantly lower than that of Kraton G over the entire frequency range investigated. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 2235–2243, 1999     

Beiträge zur Chemie des Phosphors. 136 [1]. 31P-Kernresonanzspektren und Struktur der 1,3-Dihalogen-1,2,3-tri-tert-butyltriphosphane X(t-BuP)3X,X = Cl,Br, I

Contributions to the Chemistry of Phosphorus. 136. ³¹P-N.M.R. Spectra and Structure of 1,3-Dihalogen-1,2,3-tri-tert-butyltriphosphanes X(t-BuP)₃X, X = Cl, Br, I The 1,3-dihalogen-1,2,3-tri-tert-butyltriphosphanes (t-BuP)₃Cl₂ ( 1 ), (t-BuP)₃Br₂ ( 2 ), and (t-BuP)₃I₂ ( 3 ), which are formed in the halogenating ring cleavage of tri-tert-butyl-cyclotriphosphane, (t-BuP)₃, by halogens or halogen compounds, favour the erythro, threo configuration by steric reasons. However, the erythro, erythro configurated diastereomer, whose stability depends on the size of the halogen substituents and on the rate of inversion at the phosphorus atoms, is formed initially. The reaction of the erythro, erythro and erythro, threo configurated diastereomers of 1–3 with lithium aluminium hydride leads stereospecifically to the threo, threo and threo, erythro configurated diastereomers of 1,2,3-tri-tert-butyltriphosphane, H₂(t-BuP)₃ ( 4 ), respectively.     

Poly(β-pinenes) carrying one,two, and three functional end groups. II. Syntheses and characterization

Conditions for the convenient synthesis of linear poly(β-pinenes) that carry one or two tert-chloro end groups (～Cl^t) and three-arm star poly(β-pinenes) that carry three termini have been worked out. Specifically, the polymer with one ～Cl^t end group was prepared by the H₂O/BCl₃ system, whereas those with two and three ～Cl^t termini were prepared by the use of p-dicumyl chloride and sym-tricumyl chloride/BCl₃ inifer combinations. The ～Cl^t-terminated polymers were dehydro-chlorinated to yield the corresponding olefins. The molecular weights of the products were low enough to permit infrared (IR) and quantitative ¹H-NMR investigations. Poly(β-pinene-b-tetrahydrofuran) diblock copolymers have been synthesized by inducing the polymerization of tetrahydrofuran (THF) by the Pβ? Cl^t/AgCF₃SO₃ initiating system.     

Living Carbocationic Polymerization. V. Linear Telechelic Polyisobutylenes by Bifunctional Initiators

The synthesis of α,ω-di-t-chloropolyisobutylene has been accomplished by living polymerization using aliphatic and aromatic tert-diacetate initiators in conjunction with BCl₃ coinitiator in various solvents in the ?20 to ?70°C range. The living nature of the polymerizations was demonstrated with the instantaneous initiators 2,4,4,6-tetramethyl-heptane-2,6-diacetate and 1,4-di(2-propyl-2-acetate)benzene by linear [Mbar]_n versus amount of PIB formed (W _PIB) plots starting at the origin. The formation of undesirable indanyl structures that arise with the aromatic initiator can be suppressed by decreasing the temperature and the polarity of the polymerization medium (i.e., by using CH₃Cl/n-C₆H₁₄ mixtures). Living polymerization of isobutylene can also be obtained with noninstantaneous initiators, e.g., 2,5-dimethylhexane-2,5-diacetate, 2,5-dimethylhexyne-2,5-diacetate. However, with these systems the initiator efficiency is less than 100%.     

Novel star‐block polymers: Three polyisobutylene‐b‐poly(methyl methacrylate) arms radiating from an aromatic core

A series of novel three‐arm star blocks consisting of three polyisobutylene‐b‐poly(methyl methacrylate) (PIB‐b‐PMMA) diblocks radiating from a tricumyl core were synthesized, characterized, and tested. The synthetic strategy involved three steps: the synthesis of Cl^t ‐tritelechelic PIB by living cationic isobutylene (IB) polymerization, the conversion of the Cl^t termini to isobutyryl bromide groups, and the initiation of living radical methyl methacrylate (MMA) polymerization by the latter groups. The PIB and PMMA segment lengths (M_n 's) could be controlled by controlling the conditions of the living cationic and radical polymerizations of IB and MMA, respectively. Core destruction analysis directly proved the postulated three‐arm microarchitecture. The structures of the products were analyzed by ¹H NMR and Fourier transform infrared spectroscopies, and their thermal properties were analyzed by differential scanning calorimetry and thermogravimetric analysis. The presence of a low‐ and a high‐temperature glass transition (T_g,PIB ∼ −63°C, T_g,PMMA ∼ 120°C) indicated a phase‐separated micromorphology. Stress/strain analysis showed a tensile strength of up to ∼ 22.9 MPa and an elongation of ∼ 200%. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 706–714, 2000     

Polyisobutylene-containing block polymers by sequential monomer addition. IV. New triblock thermoplastic elastomers comprising high Tg styrenic glassy segments: Synthesis,characterization and physical properties

New linear triblock thermoplastic elastomers (TPEs) comprising a rubbery polyisobutylene (PIB) midblock flanked by two glassy endblocks of various styrenic polymers have been synthesized by living carbocationic polymerization by sequential monomer addition. First isobutylene (IB) was polymerized by a bifunctional tert-ether (dicumyl methyl ether) initiator in conjunction with TiCl₄ coinitiator in CH₃Cl/methylcyclohexane (MeCHx) (40/60 v/v) solvent mixtures at ?80°C. After the living narrow molecular weight distribution PIB midblock ( = 1.1–1.2) has reached the desired molecular weight, the styrenic monomers together with an electron pair donor (ED) and a proton trap (di-tert-butylpyridine, DtBP) were added to start the blocking of the glassy segments from the living ⊕PIB⊕ chain ends. While p-methylstyrene (pMeSt), p-t-butylstyrene (ptBuSt) and indene (In) gave essentially 100% blocking to the corresponding glassy endblocks, the blocking of 2,4,6-trimethylstyrene (TMeSt) and α-methylstyrene (αMeSt) were ineffective. Uncontrolled initiation by protic impurities was prevented by the use of DtBP. In the simultaneous presence of DtBP and the strong ED N,N-dimethylacetamide (DMA), TPEs with good mechanical properties (10–20 MPa tensile strength, 300–600% elongation) were prepared. The products exhibit a low and a high temperature T_g characteristic of phase separated rubbery and glassy domains. The service temperature of these new TPEs exceeds that of PSt–PIB–PSt triblock copolymers due to the higher T_gs (PpMeSt = 108, PptBuSt = 142 and PIn = 220–240°C) of the outer blocks. The T_g of the glassy blocks can be regulated by copolymerizing two styrene derivatives; a triblock copolymer with outer blocks of poly(pt-butylstyrene-co-indene) showed a single glassy transition T_g = +165°C, i.e., in between that of PptBuSt and PIn. Virgin TPEs have been repeatedly compression molded without deterioration of physical properties. The high melt flow index obtained with a TPE containing PptBuSt endblocks suggests superior processability relative to those with PSt end-blocks. The tensile strength retention at 60°C of the former TPE is far superior to that of a PSt–PIB–PSt triblock of similar composition.     

Das erste Oxatetraphospholan, (PBut)4O

Contributions to the Chemistry of Phosphorus. 244. The First Oxatetraphospholane, (PBu^t)₄O Under suitable conditions, the reaction ot tri‐tertbutylcyclotriphosphane, (PBu^t)₃, with di‐tert‐butylperoxide gives rise to a mixture of 2,3,4,5‐tetra‐tert‐butyl‐1,2,3,4,5‐oxatetraphospholane, (PBu^t)₄O ( 1 ), and 1,2‐di‐tert‐butyl‐1,2‐di‐tert‐butoxidiphosphane, [Bu^t(Bu^tO)P]₂ ( 2 ). Both compounds have been isolated in the pure state. The oxatetraphospholane 1 is a constitutional isomer of 1,2,3,4‐Tetra‐tert‐butyl‐1‐oxocyclotetraphosphane, which has been reported recently [1]. The corresponding reaction of tetra‐tert‐butylcyclotetraphosphane furnishes only small amounts of 1 because of the kinetic stability of (PBu^t)₄. The diphosphane 2 is presumably a secondary product of primarily formed oxocyclotetraphosphanes (PBu^t)₄O_1–4. The NMR parameters of 1 and 2 are reported and discussed.     

Functional polyisobutylenes via a click chemistry approach

1‐(ω‐Azidoalkyl)pyrrolyl‐terminated polyisobutylene (PIB) was successfully synthesized both by substitution of the terminal halide of 1‐(ω‐haloalkyl)pyrrolyl‐terminated PIB with sodium azide and by in situ quenching of quasiliving PIB with a 1‐(ω‐azidoalkyl)pyrrole. Azide substitution of the terminal halide was carried out in 50/50 heptane/DMF at 90 °C for 24 h using excess azide. The 1‐(ω‐haloalkyl)pyrrolyl‐PIB precursors included 1‐(2‐chloroethyl)pyrrolyl‐PIB, 1‐(2‐bromoethyl)pyrrolyl‐PIB, and 1‐(3‐bromopropyl)pyrrolyl‐PIB. In situ quenching involved direct addition of 1‐(2‐azidoethyl)pyrrole to quasiliving PIB initiated from 5‐tert‐butyl‐1,3‐di(1‐chloro‐1‐methylethyl)benzene (bDCC)/TiCl₄ at ?70 °C in hexane/CH₃Cl (60/40, v/v). ¹H NMR analysis of the quenched product revealed mixed isomeric end groups in which PIB was attached at either C₂ or C₃ of the pyrrole ring (C₂/C₃ = 0.40/0.60). SEC indicated the absence of coupled PIB under optimized conditions, confirming exclusive mono‐substitution on each pyrrole ring. 1‐(3‐Azidopropyl)pyrrolyl‐PIB was reacted in modular fashion with various functional alkynes, propargyl alcohol, propargyl acrylate, glycidyl propargyl ether, and 3‐dimethylamino‐1‐propyne, via a Huisgen 1,3‐dipolar cycloaddition (Click) reaction, using Cu(I)Br/N,N,N′,N″,N″‐pentamethyldiethylenetriamine or bromtris(triphenylphosphine)Cu(I) as catalyst. The reactions were quantitative and produced PIBs bearing terminal hydroxyl, acrylate, glycidyl, or dimethylaminomethyl groups attached via exclusively four‐substituted triazole linkages. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 2533–2545, 2010     

Beiträge zur Chemie des Phosphors. 106. Synthese und Eigenschaften des Diphosphacyclopropans (t-BuP)2CHMe

Contributions to the Chemistry of Phosphorus. 106. Synthesis and Properties of the Diphosphacyclopropane (t-BuP)₂CHMe The new 1,2-di-tert-butyl-3-methyl-1,2-diphosphacyclopropane (1,2-di-tert-butyl-3-methyl-diphosphirane), (t-BuP)₂CHMe ( 1 ), is obtained by reacting K(t-Bu)P? P(t-Bu)K with 1,1-dichloroethane under suitable conditions. 1 can be isolated by high vacuum distillation and is stable for months when stored under inert gas at room temperature. Particularly, no dimerization to the corresponding 1,2,4,5-tetraphosphacyclohexane takes place. The NMR parameters indicate an increase of the exocyclic bond angles compared to (t-BuP)₂CH₂. The signs of all CP coupling constants have been determined by spin tickling experiments. The ²J(CCP)-coupling of the methyl group at the ring carbon depends strongly on the dihedral angle.     

Synthesis of polyisobutylene with arylamino terminal group by combination of cationic polymerization with alkylation

The controlled cationic polymerization of isobutylene (IB) initiated by H₂O as initiator and TiCl₄ as coinitiator was carried out in n‐Hexane/CH₂Cl₂ (60/40, v/v) mixture at −40 °C in the presence of N,N‐dimethylacetamide (DMA). Polyisobutylene (PIB) with nearly theoretical molecular weight (M_n = 1.0 × 10⁴ g/mol), polydispersity (M_w/M_n) of 1.5 and high content (87.3%) of reactive end groups (tert‐Chlorine and α‐double bond) was obtained. The Friedel‐Crafts alkylation of triphenylamine (TPA) with the above reactive PIB was further conducted at different reactions, such as [TPA]/[PIB], solvent polarity, alkylation temperature, and time. The resultant PIBs with arylamino terminal group were characterized by ¹H NMR, UV, and GPC with RI/UV dual detectors. The experimental results indicate that alkylation efficiency (A_eff) increased with increases in [TPA]/[PIB], reaction temperature, and reaction time and with a decrease in solvent polarity. The alkylation efficiency could reach 81.0% at 60/40(v/v) mixture of n‐Hex/CH₂Cl₂ with [TPA]/[PIB] of 4.49 at 50 °C for 54 h. Interestingly, the synthesis of PIB with arylamino terminal group could also be achieved in one pot by combination of the cationic polymerization of IB initiated by H₂O/TiCl₄/DMA system with the successive alkylation by further introduction of TPA. Mono‐, di‐ or tri‐alkylation occurred experimentally with different molar ratio of [TPA]/[PIB]. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 936–946, 2008