Synthesis Of Polyisobutylene Research Articles

Precision synthesis and characterization of thymine-functionalized polyisobutylene

A new two-step synthesis of polyisobutylene (PIB) with precisely one thymine functionality per chain (PIB-T) is reported. The primary hydroxyl-functionalized PIB (PIB-OH) precursor was prepared by direct functionalization via living carbocationic polymerization of isobutylene initiated by the α-methylstyrene epoxide/TiCl4 system. Matrix assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-ToF MS) of a low molecular weight PIB-OH precursor demonstrated the effectiveness of direct functionalization by this method. A PIB-acrylate precursor (PIB-Ac) was obtained from such a PIB-OH, and the PIB-T was subsequently prepared by Michael addition of thymine across the acrylate double bond. MALDI-ToF MS of the products verified that all polymer chains carried precisely one thymine group. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 3501–3506, 2010

Syntheses and characterization of novel biostable polyisobutylene based thermoplastic polyurethanes

Abstract The synthesis of polyisobutylene (PIB) based thermoplastic polyurethanes (TPU) with enhanced mechanical properties have been accomplished using poly(tetramethylene oxide) (PTMO) as a compatibilizer. PIB TPUs with Shore 60–100 A hardness were prepared by employing PIB diols (hydroxyallyl telechelic PIBs) for the soft segment and 4,4′-methylenebis(phenylisocyanate) (MDI) and 1,4-butanediol (BDO) for the hard segment. The TPUs exhibited number average molecular weight (Mn) in the range of 83,000–110,000 g/mol with polydispersity indices (PDIs) = 1.8–3.1. These TPUs, however, were inferior compared to commercial TPUs such as Pellethane™ (Dow Chemical Co.) as they exhibited low tensile strength (6–15 MPa) and/or ultimate elongation (30–400%). Processing of the harder compositions was also difficult and some could not be compression molded into flat sheets for testing. Differential Scanning Calorimetry (DSC) showed the presence of high melting (≥200 °C) crystalline hard segments suggesting longer – MDI–BDO – sequences than expected based on the stoichiometry. Easily processable TPUs with excellent mechanical properties (tensile strength up to 40 MPa, ultimate elongation up to 740%) were obtained by incorporating PTMO in the soft segment. Examination of PIB–PTMO TPUs with varying hard: soft compositions (20:80, 35:65 and 40:60 wt:wt) and Shore hardness (60 A, 80 A and 95 A) indicated that substituting 10–30 wt% of PIB diol with PTMO diol is sufficient to reach mechanical properties similar to Pellethanes.

Polyisobutylene-Anchored N-Heterocyclic Carbene Ligands

The synthesis of polyisobutylene (PIB)-supported N-heterocyclic carbenes (NHCs) that are useful as ligands for recoverable/recyclable organometallic complexes is described. Both PIB-bound carbenes analogous to SIMes and IMes as well as carbene precursors bound to PIB via 1,2,3-triazoles by alkyne-azide couplings are described. Both Ag(I) and Ru(II) complexes of these carbenes are shown to be phase selectively soluble in heptane. Hoveyda-Grubbs second-generation catalysts containing a PIB-supported NHC have also been used to catalyze ring-closing metathesis.

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 (Mn = 1.0 × 104 g/mol), polydispersity (Mw/Mn) 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 (Aeff) 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

Synthesis and Characterization of Novel Silicon‐Functional Polyisobutylenes and Their Applications: Polyisobutylene Brushes on Silicate Substrates via Living Cationic Polymerization

A series of novel chlorosilyl functional initiators have been prepared and applied for the first time in the living cationic polymerization of isobutylene (IB). Well‐defined polyisobutylenes (PIBs) carrying mono‐, di‐, and tri‐chlorosilyl head‐group, and a tert‐chloro end‐group were synthesized using newly designed silyl‐functional initiators in conjunction with TiCl4 in Hex:MeCl (60:40, v:v) at −80°C. End‐group analysis by 1H NMR spectroscopy verified the product structure and the survival of the Si‒Cl head‐groups during the polymerization. The chlorosilyl functional initiators and chlorosilyl functional PIBs have been employed for the synthesis of PIB brushes on planar silicate substrates by the “grafting from” and “grafting to” techniques. The products were characterized by x‐ray photoelectron spectra (XPS), atomic force microscopic (AFM), and ellipsometry. The “grafting from” approach yielded surface‐bound polymer brushes with more uniform surface and higher grafting density compared to the “grafting to” technique. The film thickness of PIB brushes formed by “grafting from” increased linearly with increasing molecular weight of PIB. In contrast, PIB brushes produced by “grafting to” gave constant thickness independent of the molecular weight of PIB.

Cationic polymerization of isobutylene initiated by diol/boron trichloride systems

Cationic polymerizations of isobutylene initiated by 2,5-dimethyl-2,5-hexane diol (HMD) and bis-para-2-hydroxy-2-propylbenzene (BPP)/BCl3 were carried out in CH2Cl2 solution at −30 °C, in presence or in absence of 2,6-ditert-butylpyridine (DtBP).IR, 1H NMR and C13 NMR analysis of the resulting polyisobutylenes (PIB) show the insertion of the diol skeleton in the polymers. GPC chromatograms show that the presence of DtPB prevents protonic initiation. The synthesis of PIB with phenolic end groups was carried out by alkylation of α, ω unsaturated oligoisobutylene in CH2Cl2 at −30 °C initiated by SnCl4. Previously,the alkylation was carried out on a model:2,2,4-trimethyl pentene (TMP). Spectroscopic analyses show that the alkylation takes place mainly on para-position. UV titration of phenyl ring and chemical titration of chlorine show that the functionality of PIB is 2.

Thermally reversible polymer systems by cyclopentadienylation. II. The synthesis of cyclopentadiene‐containing polymers

AbstractThe synthesis of polymers containing either terminal or pendant cyclopentadiene (CPD) groups has been studied. Using information obtained from model studies, the synthesis of polyisobutylenes containing a CPD terminus was accomplished by the use of the tert‐butylchloride–dimethylcyclopentadienylaluminum initiator system. Isobutylene polymerization by this system under carefully chosen conditions is essentially transfer free, and termination occurs by cyciopentadienylation. The presence of CPD end group has been established by UV spectroscopy and reaction with maleic anhydride. Selectivity toward termination by cyclopentadienylation increases with decreasing temperatures; at −41°C and low conversion (<10%) ca. 72% of the polymer chains terminate in this manner. The synthesis of polymers containing randomly distributed pendant CPD groups along the chain has been accomplished by cyclopentadienylating with dimethylcyclopentadienylaluminum chlorobutyl rubber and chlorinated poly(ethylene‐co‐propylene) (Cl‐EPM). Pendant CPD groups undergo Diels‐Alder/retro‐Diels‐Alder condensations yielding thermally reversible networks; e.g., a cyclopentadienylated Cl‐EPM was remolded three times to elastic sheets.