Alexander V. Lubnin

Comprehensive Assignments of 1H- and 13C-NMR Signals of End-Functional Polyisobutylenes Using Spin-Lattice Relaxation Times and 2D 1H- 13C Hetcor Spectroscopy

Abstract The analysis of 13C spin-lattice relaxation times (T 1′s) provides a direct method for the assignment of 13C-NMR signals of the end groups of polymers. The 13C T 1′s of polyisobutylenes bearing tert-butyl, tert-chloride, exo-olefin, alcohol, aldehyde, and acetal end groups have been determined, and all the signals in their 13C-NMR spectra were assigned according to the gradient of T 1 along the polymer chain with the minimum in the middle. The assignments are in excellent agreement with those established by other techniques, which indicates the reliability of this novel method for the characterization of various end groups in polyisobutylenes. 13C T 1 analysis has also been used to obtain assignments for internal polyisobutylene segments adjacent to aromatic initiator residues. The method provides insight into the interaction of hydroxyl end groups of alcohol-capped PIBs, and allows identification of the low molecular weight impurities in the polymers. Assignments of all the 1H-NMR signals of the...

Synthesis and characterization of aldehyde-capped polyisobutylenes

SummaryThe synthesis and characterization of linear mono- and ditelechelic polyisobutylenes (PIBs) carrying terminal primary aldehyde groups are described. The synthesis starts by chlorine terminated PIBs (PIB−Cl and Cl−PIB−Cl) prepared by inifering or living carbocationic polymerization. These starting materials were dehydrochlorinated to vinylidene (∼CH2−C(CH3)=CH2) terminated PIBs and hydroformylated with CO/H2 in the presence of a rhodium catalyst. According to NMR (500 MHz) and GPC analyses, the transformations are selective and demonstrably quantitative. The structures of these novel polymers are: I view of the rich chemistry of the aldehyde group, these materials are valuable intermediates.

The Microstructure of Poly(Isobutylene-co-p-Methylstyrene) by NMR Spectroscopy

Abstract The microstructure of isobutylene-para-methylstyrene (IB-pMeSt) copolymers was studied by NMR spectroscopy. 1H- and 13C-NMR spectra were used to obtain overall copolymer compositions. 13C-NMR signals were assigned in terms of triad monomer sequences, and triad distributions were obtained over a wide copolymer composition range. According to statistical tests, the IB-pMeSt copolymerization cannot be described by zero- (Bernoullian) or first-order Markov models because reactivity ratios r IB and r pMeSt were found to change with the monomer feed composition. Additional insight into the microstructure of IB-pMeSt copolymers was gained by calculating sequence numbers, run numbers, and sequence lengths from triad distributions. Further, the Kelen-Tudos plot showed a distinct curvature indicating that the Kelen-Tudos method, applied over the entire monomer feed composition range, cannot give meaningful reactivity ratios for this monomer pair. Evidently the simple two-parameter Mayo-Lewis model is inade...

Designed T- and comb-shaped copolymers of poly(ethylene oxide) and polyisobutylene

The synthesis, characterization, and select emulsification properties of T- and comb-shaped sequential copolymers comprising a poly(ethylene oxide) (PEO) backbone carrying one or multiple polyisobutylene (PIB) branches linked by acetal groups are described. Conditions have been developed under which PIBs carrying an aldehyde end-group (PIB-CHO) react with commercially available PEOs carrying one or two hydroxyl termini (MeO-PEO-OH and HO-PEO-OH) to yield MeO-PEO-OCH(PIB)O-PEO-OMe or HO-PEO-O(CH(PIB)O-PEO-O)H, respectively. The microarchitecture and composition of these copolymers can be influenced by the CHO/OH ratio and the molecular weight of the prepolymers. These sequential copolymers forms very stable oil-in-water emulsions

Identification of Initiator Fragments in Polyisobutylene by Nmr Spectroscopy

Abstract Deuterated polyisobutylenes carrying protonated initiator fragments were prepared by the living polymerization technique employing perdeuterated isobutylene [CD2=C(CD3)2] and select protonated initiators (see Scheme 1). The polymers were analyzed by 1H- and 13C-NMR spectroscopy, and the resonances due to the protic initiator fragments were unequivocally assigned. The assignments of 13C-NMR signals were affected by the distortionless enhancement by polarization transfer mode of spectra accumulation.

A new iodine-free initiating system for the living polymerization of isobutyl vinyl ether

SummaryA new iodine-free initiating system, MeCH(Oi-Bu)Cl/n-Bu4NTiCl5, was found to induce the living carbocationic polymerization (LC⊕Pzn) of isobutyl vinyl ether (IBuVE) at-20 °C in CH2Cl2. Using this system, poly(isobutyl vinyl ether) (PIBuVE) with the theoretical molecular weights (up toca. 45,000) calculated from the initiator/monomer input and narrow molecular weight distribution (Mw/Mn < 1.1) can be readily obtained. The polymerization is first order in the monomer. The coinitiating function ofn-Bu4NTiCl5 may be due to a salt effect or to its Lewis acid character. An attempt for the synthesis of the polyisobutylene (PIB)-PIBuVE block copolymer has failed most likely becausen-Bu4NTiCl5 is unable to activate the ∼C(CH3)2-Cl bond of the PIB termini.

Initiation of living polymerization of isobutyl vinyl ether by the “H2O”/n-Bu4NTiCl5 system

SummaryLiving carbocationic polymerization (LC⊕Pzn) of isobutyl vinyl ether (IBuVE) is readily initiated by adventitious moisture (“H2O”) in the presence ofn-Bu4NTiCl5 in CH2Cl2 solvent at-20 °C to yield high molecular weight polymers (up to 100,000 g/mole) with narrow molecular weight distributions

Star polymers having a well-defined siloxane core and multiple polyisobutylene arms and a method for the synthesis thereof

\bar M_W /\bar M_N = 1.1