MALDI‐TOF MS characterization of dihydroxy telechelic polyisobutylene

MALDI‐TOF MS characterizations of dihydroxy telechelic polyisobutylene is reported. Dichloro telechelic polyisobutylene (Cl—PIB—Cl) was synthesized by means of living cationic polymerization using p‐dicumyl chloride/BCl₃/DMSO initiating systems. The resulting polymer was functionalized by polymer analogous reactions to yield dihydroxy telechelic polyisobutylene (HO—PIB—OH). It was then investigated by MALDI‐TOF MS in the cation mode using 1,8‐dihidroxy‐9(10H)‐anthracenone (dithranol)/CF₃COOAg matrix. The MALDI TOF MS spectra showed an increase in mass by 56 amu units attributed to the isobutylene monomer increment. The endgroups of HO—PIB—OH were determined. A good agreement was also found between the calculated isotope distributions and the isotope distributions determined by means of MALDI.     

Direct functionalization of polyisobutylene by living initiation with α‐methylstyrene epoxide

This article describes the synthesis and characterization of polyisobutylene (PIB) carrying one primary hydroxyl head group and a tertiary chloride end group, [Ph? C(CH₃)(CH₂OH)–PIB–CH₂? C(CH₃)₂Cl] prepared with direct functionalization via initiation. The polymerization of isobutylene was initiated with the α‐methylstyrene epoxide/titanium tetrachloride system. Living conditions were obtained from ?75 to ?50 °C (198–223 K). Low molecular weight samples (number‐average molecular weight ～ 4000 g/mol) were prepared under suitable conditions and characterized by Fourier transform infrared and ¹H NMR spectroscopy. The presence of primary hydroxyl head groups in PIB was verified by both methods. Quantitative Fourier transform infrared with 2‐phenyl‐1‐propanol calibration and ¹H NMR performed on both the hydroxyl‐functionalized PIB and its reaction product with trimethylchlorosilane showed that each polymer chain carried one primary hydroxyl head group. The synthetic methodology presented here is an effective and simple route for the direct functionalization of PIB. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 1005–1015, 2002     

New telechelic polymers and sequential copolymers by polyfunctional initiator-transfer agents (inifers). XXX. Synthesis and quantitative terminal functionalization of α,ω-diarylpolyisobutylenes

Novel aromatic-telechelic polyisobutylenes were prepared and characterized: α,ω-diphenylpolyisobutylene, α-phenyl-ω-tolylpolyisobutylene, and α,ωditolylpolyisobutylene. The syntheses involved the preparation of asymmetric telechelic prepolymers (α-phenyl-ω-tert-chloropolyisobutylene and α-tolyl-ω-tert-chloropolyisobutylene) by the minifer method and quantitative alkylation of benzene and toluene by the prepolymer. The terminal aromatic rings of these telechelic polyisobutylenes were quantitatively nitrated, acetylated, and chlorosulfonated and a series of further novel telechelic products was obtained. Characterization of these derivatives provided additional proof for the telechelic structure of the starting prepolymers. The quantitative reduction of nitroaryl-telechelic polyisobutylene by SnCl₂/HCl led to aminoaryl-telechelic polyisobutylene which was used to cure bisphenol-A diglycidyl ether. These new flexible epoxy networks exhibited outstanding heat and hydrolytic stability combined with satisfactory mechanical properties.     

Polyisobutylene‐based polyurethanes. VIII. Polyurethanes with ‐O‐S‐PIB‐S‐O‐ soft segments

We describe the synthesis, characterization, and select properties of a novel polyurethane (PU) prepared using a new polyisobutylene diol, HO‐CH₂CH₂‐S‐PIB‐S‐CH₂CH₂‐OH, soft segment and conventional hard segments. The diol is synthesized by terminal functionalization of ally‐telechelic PIB followed by low‐cost thiol‐ene click chemistry. Properties of ‐S‐ containing PU (PIB_S‐PU) containing 72.5% PIB were investigated and compared to similar PUs made with HO‐PIB‐OH (PIB_O‐PU). Hydrolytic resistance was studied by contact with phosphate‐buffered saline, oxidative resistance by immersing in concentrated HNO₃, and metal ion oxidation resistance by exposure to CoCl₂/H₂O₂. Hydrolytic and oxidative resistances of PIB_S‐PU and PIB_O‐PU are similar and superior to a commercial PDMS‐based PU, Elast‐Eon? E2A. According to ¹H NMR spectroscopy the ‐S‐ in PIB_S‐PUs remained unchanged upon treatment with HNO₃, however, oxidized mainly to ‐SO₂‐ by CoCl₂/H₂O_2. Static mechanical properties of PIB_S‐PU and PIB_O‐PU are similar, except creep resistance of PIB_S‐PU is surprisingly superior. The thermal stability of PIB_S‐PUs is ～15 °C higher than that of PIB_O‐PU. FTIR spectroscopy indicates H bonded S atoms (N‐H…S) between soft and hard segments, which noticeably affect properties. DSC and XRD studies suggest random low‐periodicity crystals dispersed within a soft matrix. Energy dispersive X‐ray spectroscopy–scanning electron microscopy indicates homogeneous distribution of S atoms on PIB_S‐PU surfaces. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 1119–1131     

Highly Effective and Green Catalytic Approach Toward α,ω‐Dihydroxy‐Telechelic Poly(trimethylenecarbonate)

α,ω‐Dihydroxy‐telechelic poly(trimethylenecarbonate), HO‐PTMC‐OH, is synthesized from the controlled “immortal” ring‐opening polymerization (ROP) of trimethylene carbonate under mild conditions (bulk, 60 °C), using ZnEt₂ or, more efficiently, [(BDI)Zn(N(SiMe₃)₂)] (BDI = CH(CMeNC₆H₃‐2,6‐iPr₂)₂) as catalyst precursor, in the presence of a diol HO‐R‐OH (R = (CH₂)₂ or CH₂C₆H₄CH₂; 0.5–10 equiv. vs Zn) acting both as co‐initiator and chain transfer agent. Alternatively, HO‐PTMC‐OH is prepared upon hydrogenolysis of HO‐PTMC‐OCH₂Ph, initially prepared from the ROP of TMC using the [(BDI)Zn(N(SiMe₃)₂)]/PhCH₂OH system, under smooth operating conditions using Pd/charcoal. Well‐defined dihydroxy‐functionalized PTMCs of molar mass ranging from = 2 000 to 109 500 g · mol⁻¹ were thus quantitatively obtained and fully characterized by NMR, MALDI‐TOF‐MS and SEC analyses. The versatility of this “immortal” ROP allows the preparation of alike α,ω‐functional polyester such as linear HO‐poly(lactide)‐OH, as well as star polymers such as the glycerol‐based PTM‐OH₃.

     

Low‐cost bifunctional initiators for bidirectional living cationic polymerization of olefins. III. centrally functionalized polyisobutylenes

Allyl‐telechelic polyisobutylene (A‐PIB‐A) produced by the bis‐benzocyclobutane dichloride (bBCB‐diCl) initiator contains the bis‐benzocyclobutane (bBCB) fragment at the center of the macromolecule (A‐PIB‐bBCB‐PIB‐A). Thermolysis of A‐PIB‐bBCB‐PIB‐A quantitatively converts the central bBCB fragment to a substituted conjugated tetraene (A‐PIB‐tetraene‐PIB‐A). The structure of A‐PIB‐tetraene‐PIB‐A was anticipated from small molecule models and identified/quantitated by ¹H NMR spectroscopy. This is the first time a reactive functional group was introduced at the statistical center of a (telechelic) PIB. Subsequently, the A‐PIB‐tetraene‐PIB‐A was peroxidized to an epoxy derivative. Reaction of the A‐PIB‐tetraene‐PIB‐A with HSCH₂CH₂OH produced HOCH₂‐telechelic PIB containing a central  CH₂OH function, and hydrosilation with HSi(Me₂)‐O‐Si(Me₂)H produced SiH‐telechelic PIB with a central  SiH function. Reactions with maleic anhydride, tetracyanoethylene, butyl lithium, and potassium permanganate have also been examined. In sum, A‐PIB‐bBCB‐PIB‐A and A‐PIB‐tetraene‐PIB‐A are useful intermediates for the synthesis of novel PIB‐based materials for various end uses under investigation. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2018 , 56, 1140–1145     

New telechelic polymers and sequential copolymers by polyfunctional initiator-transfer agents (inifers). II. Synthesis and characterization of α,ω-di(tert-chloro)polyisobutylenes

Detailed understanding of the mechanism of initiation and chain transfer in BCl₃-coinitiated isobutylene polymerization led to the efficient synthesis of symmetric telechelic polyisobutylenes carrying ～CH₂C(CH₃)₂Cl groups at either end of the molecule Cl-PIB-Cl. The synthesis is based on the use of inifers, i.e., bifunctional initiator-transfer agents that effect controlled initiation and propagation in the absence of chain transfer to a monomer. Specifically, the synthesis of Cl-PIB-Cl was achieved by the p-dicumyl chloride/BCl₃/isobutylene/CH₂Cl₂ system. According to the inifer mechanism each Cl-PIB-Cl contains two terminal tertiary chlorines and one phenyl group at the interior of the chains. The structure of this new symmetric telechelic polymer has been established by detailed characterization studies including a sensitive new gel permeation chromatography (UV plus RI) analysis method, ¹H-NMR, kinetic experiments, and chemical derivatization. The Cl-PIB-Cl molecule is a key intermediate for the synthesis of hosts of new materials, e.g., triblock copolymers, α,ω-diolefins, and α,ω-difunctional polymers.     

Polyisobutylene‐based polyurethanes X: PU nanocomposites with s‐containing soft segments

Sulfur‐containing polyisobutylene (PIB)‐based polyurethane nanocomposite (PIB_s‐PU/NC) was synthesized using HO? CH₂CH₂? S? PIB? S? CH₂CH₂? OH for the soft segment, conventional hard segments of MDI and BDO, and organically modified montmorillonite (OmMMT) nanolayers. The properties of PIB_s‐PU/NC containing 72.5% PIB and 0.5% OmMMT were studied and contrasted with unmodified PIB_s‐PU. PIB_s‐PU/NC produces colorless optically clear films exhibiting enhanced tensile strength, elongation, oxidative–hydrolytic stability, and creep resistance relative to that of PIB_s‐PU. FTIR spectroscopy indicates H bonded S atoms between soft and hard segments, and OmMMT nanolayers. DSC and XRD suggest randomly dispersed low‐periodicity crystals and urea groups between galleries. We propose that minute amounts of OmMMT nanolayers become covalently attached to polyurethane chains and beneficially affect properties by acting as co‐chain extender/reinforcing filler. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 2760–2765     

Analysis of 1H-NMR spectra of various end-functionalized polyisobutylenes

¹H-NMR spectra of various telechelic (i.e., ～ CH₂C(CH₃)₂Cl, ～ CH₂C(CH₃)?CH₂, ～ CH?C(CH₃)₂, and ～ CH₂CH(CH₃)CH₂OH capped) polyisobutylenes (PIB) have been analyzed. The products were prepared by living carbocationic polymerization followed by end-group functionalization. Shielding and deshielding effects strongly influence the ¹H-NMR spectra of these products. Inductive effects (chlorine-ended PIBs), magnetically anisotropic end-groups (olefin groups and phenyl rings), allylic coupling (olefin end-groups), chirality (hydroxyl end-groups), and the interaction of these effects on the ¹H-NMR spectra are discussed. Numerous heretofore unidentified resonances have been assigned and better insight into the detailed structure of end-functionalized PIBs has been obtained. © 1994 John Wiley & Sons, Inc.     

Synthesis and mass spectrometry characterization of centrally and terminally amine‐functionalized polyisobutylenes

This article reports the facile synthesis of novel terminally and centrally functionalized polyisobutylenes (PIBs) and the detailed characterization of the products by various mass spectrometry techniques. Specifically, H? PIB? CH₂? C(OH)CH₃? CH₂? NHCH₃ and [H? PIB? CH₂? CH(OH)CH₃? CH₂]₂? NCH₃ were synthesized by the quantitative epoxidation of H? PIB? CH₂? C(CH₃)?CH₂ and the subsequent conversion of the resulting epoxide with excess CH₃NH₂. Quaternization with CH₃Cl of these mixtures of secondary and tertiary amines yielded exclusively H? PIB? CH₂? C(OCH₃)CH₃? CH₂? N(CH₃)₂ from the secondary amine, whereas the tertiary (centrally functionalized) amine remained unchanged. Tandem mass spectrometry experiments provided unique insight into the precise connectivity of the functional end groups added to the PIB frame. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 946–958, 2005     

IR spectra of long-chain α,ω-alkanediols: 1,22-docosanediol and 1,44-tetratetracontanediol

The IR absorption spectra of α,ω-alkanediols with different chain lengths, HO(CH₂)₂₂OH and HO(CH₂)₄₄OH, in the spectral range of 400–5000 cm^?1 are analyzed. The assignment of numerous absorption bands to vibration modes in short methylene sequences and terminal hydroxyl groups is suggested. The splitting of IR absorption bands into doublets at 720–730 cm^?1 (rocking vibrations of CH₂ groups) and 1463–1473 cm^?1 (bending vibrations of CH₂ groups) testifies that the crystal unit subcells in the lamellae of alkanediols are orthorhombic with parameters typical of normal hydrocarbons. The specific features of absorption bands due to O-H stretching and C-O-H bending vibrations have been analyzed. These bands appear during formation of lengthy associates from hydrogen bonds formed by hydroxyl groups on the surface of elementary lamellae. A sharp increase in the intensity of the absorption bands in progression of C-C stretching and CH₂ wagging vibrations due to the anharmonic Fermi resonance with the stretching vibrations of C-O groups in the terminal hydroxyl groups has been detected.     

The polymerization of isobutylene by AlCl3 in CH2Cl2 and the role of CH2Cl2 in the initiation reaction

A solution of AlCl₃ in CH₂Cl₂ prepared in advance was used 18 days after the mixing of the components as an initiation system in the polymerization of isobutylene performed in CH₂Cl₂ in the temperature range between ?10 and ?20°C. The ¹H-NMR analysis of polyisobutylene (PIB) samples synthesized to low and high conversion showed that it is the initiation reaction and not the transfer reaction to dichloromethane that is responsible for the ? CH₂Cl endgroup in the polymer chain. In case of the transfer to monomer formation of PIB with internal terminal unsaturation [PIB? CH?C(CH₃)₂] is preferred to external unsaturation [PIB? CH₂(CH₃)C?CH₂]. The solutions of AlCl₃ in CH₂Cl₂ showed an absorption band at λ_max = 302 nm.     

Cationic Polymerization with Boron Halides. VIII. Synthesis of (CH3)2C = CHCH2-Polyisobutylene-CI Prepolymer and Subsequent Preparation of (CH3)2C = CHCH2-Poly(isobutylene-b-styrene) and (CH3)2C = CHCH2-Poly(isobutylene-b-α-methylstyrene)

Asymmetric telechelic polyisobutylene, α-PIB-ω), carrying the olefinic head group α = (CH₃)₂ C[dbnd]CHCH₂- and tertiary chlorine endgroup ω = -C(CH₃)₂Cl has been synthesized by the use of the (CH₃)₂C[dbnd]CHCH₂Cl/BCl₃ initiating system. Highest yields were obtained by using methylene chloride diluent at about ?50°C. The presence and position of the olefinic head-group was proven by epoxidation/titration and epoxidation/cleavage. The presence and position of a tertiary chlorine endgroup was proven by initiating block polymerization of a second monomer, such as styrene or α-methylstyrene, by using the asymmetric telechelic polyisobutylene prepolymer in conjunction with Et₂AlCl coinitiator. According to I/DP versus 1/[M] plots obtained in model block copolymerization experiments, with the use of the tert-BuCl/Et₂AlCl initiating system at ?30°C, significant chain transfer to monomer occurs during blocking of styrene; however, monomer transfer is negligible during blocking of α-methylstyrene. Thus, under suitable conditions head-functionalized block copolymers (CH₃)₂C[dbnd]CHCH₂-PIB-b-PαMeSt virtually free of homopolymer contaminants can be obtained.     

Synthesis and characterization of novel amphiphilic block copolymers di‐, tri‐, multi‐, and star blocks of PEG and PIB

A simple but efficient strategy has been developed for the synthesis of novel di‐, tri‐, multi‐, and star‐block copolymers comprising poly(ethylene glycol) (PEG) and polyisobutylene (PIB) blocks. The synthesis principle involves the coupling of appropriately terminally functionalized PEG and PIB sequences, specifically the hydrosilation of mono‐, di‐, and tetra‐allyl‐telechelic PEGs (PEG‐allyl, allyl‐PEG‐allyl, and C(‐PEG‐allyl)₄ by mono‐ and di‐Si(CH₃)₂H telechelic PIBs (PIB‐SiH and HiS‐PIB‐SiH). Representative block copolymers, for example, PEG‐PIB, PIB‐PEG‐PIB, (‐PIB‐PEG‐)_n, and C(‐PEG‐PIB)₄ have been assembled and their structures determined by ¹H and ¹³C NMR spectroscopy. The bulk and surface morphology of select triblocks have been investigated by DSC and AFM and the findings interpreted in terms of phase‐separated PEG and PIB microdomains. The swelling behavior in water of various block copolymers also has been studied. Block copolymers containing 50–70 wt % PIB produce hydrogels, the integrity of which is maintained by physical crosslinks by PIB segments. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 3200–3209, 2000     

Structure and formation of gaseous [C4H6O]+˙ ions: 1—The enolic ions [CH2C(OH)?CHCH2]+˙ and [CH2CH?CHCH(OH)]+˙ and their relationship with their keto counterparts

The [C₄H₆O]^+˙ ion of structure [CH₂?CHCH?CHOH]^+˙ (a) is generated by loss of C₄H₈ from ionized 6,6-dimethyl-2-cyclohexen-1-ol. The heat of formation ΔH_f of [CH₂?CHCH?CHOH]^+˙ was estimated to be 736 kJ mol^?1. The isomeric ion [CH₂?C(OH)CH?CH₂]^+˙ (b) was shown to have ΔH_f, ? 761 kJ mol^?1, 54 kJ mol^?1 less than that of its keto analogue [CH₃COCH?CH₂]^+˙. Ion [CH₂?C(OH)CH?CH₂]^+˙ may be generated by loss of C₂H₄ from ionized hex-1-en-3-one or by loss of C₄H₈ from ionized 4,4-dimethyl-2-cyclohexen-1-ol. The [C₄H₆O]^+˙ ion generated by loss of C₂H₄ from ionized 2-cyclohexen-1-ol was shown to consist of a mixture of the above enol ions by comparing the metastable ion and collisional activation mass spectra of [CH₂?CHCH?CHOH]^+˙ and [CH₂?C(OH)CH?CH₂]^+˙ ions with that of the above daughter ion. It is further concluded that prior to their major fragmentations by loss of CH₃˙ and CO, [CH₂?CHCH?CHOH]⁺˙ and [CH₂?C(OH)CH?CH₂]^+˙ do not rearrange to their keto counterparts. The metastable ion and collisional activation characteristics of the isomeric allenic [C₄H₆O]^+˙ ion [CH₂?C?CHCH₂OH]^+˙ are also reported.     

α, ω-Alkan-bis-dimethylarsansulfide und -selenide,eine neue Klasse von Liganden

α ω-Alkane-bis-dimethylarsine Sulfides and Selenides, a Novel Class of Ligands The reaction of α,ω-alkane-bis-dimethylarsanes (CH₃)₂As? (CH₂)_n? As (CH₃)₂ with sulfur and selenium results in formation of the sulfides and selenides, respectively, (CH₃)₂As(X)? (CH₂)_n? As(CH₃)₂ or (CH₃)₂As(X)? (CH₂)_n? As(X)(CH₃)₂ (X = S, Se), which form chelat-complexes with the salts CoX₂ · 6 H₂O (X = Cl^?, Br^?, I^?, NO₃^?). The UV-spectra of the complexes are presented and discussed.     

The [CH5NO]+ ˙ potential energy surface: Distonic ions,lon-dipole complexes and hydrogen-bridged radical cations

By combining results from a variety of mass spectrometric techniques (metastable ion, collisional activation, collision-induced dissociative ionization, neutralization-reionization spectrometry, ²H, ¹³C and ¹⁸O isotopic labelling and appearance energy measurements) and high-level ab initio molecular orbital calculations, the potential energy surface of the [CH₅NO]^{+ ˙} system has been explored. The calculations show that at least nine stable isomers exist. These include the conventional species [CH₃ONH₂]^{+ ˙} and [HO? CH₂? NH₂]^{+ ˙}, the distonic ions [O? CH₂? NH₃]^{+ ˙}, [O? NH₂? CH₃]^{+ ˙}, [CH₂? O(H)? NH₂]^{+ ˙}, [HO? NH₂? CH₂]^{+ ˙}, and the ion-dipole complex CH₂?NH₂⁺ …? OH˙. Surprisingly the distonic ion [CH₂? O? NH₃]^{+ ˙} was found not to be a stable species but to dissociate spontaneously to CH₂?O + NH₃^{+ ˙}. The most stable isomer is the hydrogen-bridged radical cation [H? C?O …? H …? NH₃]^{+ ˙} which is best viewed as an immonium cation interacting with the formyl dipole. The related species [CH₂?O …? H …? NH₂]^{+ ˙}, in which an ammonium radical cation interacts with the formaldehyde dipole is also a very stable ion. It is generated by loss of CO from ionized methyl carbamate, H₂N? C(?O)? OCH₃ and the proposed mechanism involves a 1,4-H shift followed by intramolecular ‘dictation’ and CO extrusion. The [CH₂?O …? H …? NH₂]^{+ ˙} product ions fragment exothermically, but via a barrier, to NH₄^{+ ˙} HCO^…? and to H₃N? C(H)?O^{+ ˙} H˙. Metastable ions [CH₃ONH₂]^+…? dissociate, via a large barrier, to CH₂?O + NH₃⁺ + and to [CH₂NH₂]⁺ + OH˙ but not to CH₂?O^{+ ˙} + NH₃. The former reaction proceeds via a 1,3-H shift after which dissociation takes place immediately. Loss of OH˙ proceeds formally via a 1,2-CH₃ shift to produce excited [O? NH₂? CH₃]^{+ ˙}, which rearranges to excited [HO? NH₂? CH₂]^{+ ˙} via a 1,3-H shift after which dissociation follows.     

Zum Mechanismus Massenspektrometrischer Fragmentierungsreaktionen. XVI—hydrid-Wanderungen bei der Fragmentierung von αω-Dimethoxyalkyl-Ionen

The isomerization and fragmentation of α,ω-dimethoxyalkyl ions a (CH₃OCH₂(CH₂)_n- CH⁺OCH₃, n = 1-6) has been investigated by deuterium labelling. It is shown that a isomerizes to ion a' by hydride transfer from the ω-CH₂ group to the positive charge at the α-C-atom before elimination of methanol. Both methoxy groups are lost as methanol. The amount of isomerization can be deduced from alkene elimination from [a ? CH₃OH]+ ions in deuterated derivatives of a. On average at 70 eV three rearrangement steps involving hydride transfer are observed.     

Polyisobutylene-containing block polymers by sequential monomer addition. X. Synthesis of poly(α-methylstyrene-b-isobutylene-b-α-methylstyrene) thermoplastic elastomers

Preparatory to triblock synthesis experiments, the cationic polymerization of α-methylstyrene (αMeSt) was investigated using the 2-chloro-2,4,4-trimethylpentane (TMPCI)/TiCl₄ initiating system in the presence of triethylamine (Et₃N) as electron donor (ED) and CH₃Cl/n-hexane mixed solvent in the ?80 to ?40°C range. Conversions are influenced by temperature, [TiCl₄], [Et₃N], and [αMeSt]. The polymerization of αMeSt is living at ?80°C: Both termination and chain transfer to monomer are frozen out, however, initiation is slow relative to propagation. Highly syndiotactic (>94%) Pα Mest was obtained. At?60deg;C initiator efficiency is ca. 100%, but termination becomes evident. Et₃N may act both as Ed and as proton scavenger. Novel poly(α-methystyrene-b-isobutylene-b-α-methylstyrene) (PαMeSt-PIB-PαMeSt) triblocks have been synthesized by adding αMeSt to biliving polyisobutylene carbocations (⊕PIB⊕) in the ?80 to ?40°C range. The effects of temperature, solvent polarity, and [Et₃N] on the block copolymerization have been investigated. At ?80°C, the rate of crossover from ⊕PIB⊕ to αMeSt is lower than that of propagation of PαMeSt⊕, so that the triblock is contaminated by PIB and PIB-b-PαMeSt. At ?60°C, crossover occurs preferentially. The rate of propagation relative to that of crossover is also reduced by lowering the solvent polarity and increasing the [Et₃N]. High crossover efficiency and blocking efficiency can be obtained under optimum blocking conditions. The triblocks are novel thermoplastic elastomers (TPEs). © 1994 John Wiley & Sons, Inc.     

Poly(ether ketone)–polyisobutylene block copolymers: Synthesis and phase behavior

Telechelic poly(ether ketone)s (PEKs) and polyisobutylenes (PIBs) were combined to form PIB? PEK? PIB triblock copolymers and (PIB? PEK)_n multiblock copolymers via the formation of urea linkages. Monovalent and bivalent amino telechelic PIBs were prepared quantitatively from allyl telechelic PIBs by a newly developed reaction sequence featuring nucleophilic reaction steps. Telechelic PEK? NCO polymers were prepared from the corresponding amino telechelic PEKs via a reaction with diphosgene. The highly reactive PEK? NCO and PIB? NH₂ telechelics formed PEK? PIB block copolymers only quantitatively when appropriately reactive primary amino groups were present on the amino telechelic PIBs. The obtained block copolymers were microphase‐separated and featured mostly lamellar structures, as determined by small‐angle X‐ray scattering (SAXS). Temperature‐dependent SAXS measurements revealed ordered polymers in the melt up to 210 °C. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 188–202, 2005