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Polyisobutylene was synthesized using 2-chloro-2,4,4-trimethylpentane (TMPCl) as an initiator and TiCl4 as a coinitiator. After taking a base sample, the living cation was reacted with 5 equivalents of (4-vinylphenyl)dimethylsilane (VPDMSi). It was observed that the cation preferred reduction by hydride elimination from VPDMSi compared to electrophilic addition of even a single vinyl group. It was postulated that the reduction of the cation in presence of strong Lewis acid such as TiCl4 occurs readily before addition of cation to vinyl group. Thus saturated polyisobutylene was obtained with a terminal hydrogen group instead of chlorine group which is produced by conventional cationic polymerization.

We explored a new synthetic strategy for ultra-high molecular weight long-chain branched (LCB) polymers with equal spacing between adjacent branch points. This method can synthesize LCB polystyrene (LCB-PS) with total molecular weight of 4.9 million g/mole, 16 branches of 140 kg/mole and polydispersity index of 1.5. The introduction of multiple branch points with long side chains allows the LCB-PS to resist the elastic-driven decohesion. Even after a large step extension of stretching ratio λ = 7.4, the specimen would not undergo elastic breakup that occurs in linear PS even at λ = 2.7. These LCB-PSs are also extraordinarily more stretchable during startup uniaxial extension, with the maximum engineering stress emerging at stretching ratio λ max ≈ 4 M bb / M e , where Mbb is the molecular weight of backbone and Me is the molecular weight between entanglements.

The model reaction of n-butyllithium with excess (11 M equivalents) 1,1-diphenylethylene (DPE) was reinvestigated using modern characterization techniques including SEC, one dimensional and two dimensional nuclear magnetic resonance (1D and 2D NMR) spectroscopy and electrospray ionization mass spectrometry (ESI MS). The products were the monoadduct, 1,1-diphenylhexane (nBuDPEH), and the diadduct, 1,1,3,3-tetraphenyloctane [nBu(DPE)2H], formed in 62 mol% and 38 mol% yields, respectively, as determined by SEC and 1H NMR spectroscopy. The 1H NMR spectrum of 1,1,3,3-tetraphenyloctane exhibited a terminal methine triplet resonance at δ 3.71 ppm that was uniquely coupled to the adjacent methylene doublet resonance at δ 3.09 ppm, located between the two carbons, each bonded to two phenyl groups [–C(C6H5)2-CH2-CH(C6H5)2. All of the characteristic 1H and 13C NMR resonances for both adducts were assigned using 2D NMR spectroscopic methods. The diadduct, nBu(DPE)2H, exhibited unique 13C NMR resonances at δ 50.79 ppm for the quaternary carbon resonance [CH2-C(C6H5)2−CH2], and at δ 43.74 ppm for the methylene group isolated between the two carbons, each bonded to two phenyl groups [–C(C6H5)2-CH2-CH(C6H5)2].

For the first time, the scope of Fisher esterification has been extended to fullerene derivatives to improve the synthesis of alkyne-functionalized fullerenes (fullerynes) using 1-chloronaphthalene as a solvent and a specially-designed, home-made reactor to promote high yield. The design allows for higher solubility of fullerene derivatives and a continuous azeotropic distillation for the removal of water to drive the reaction to completion with yields >90%. Both fullerynes (Fulleryne01 and Fulleryne02) were found to “click” to polymers, such as azide-functionalized poly(ɛ-caprolactone) (PCL-N 3 ), in high efficiency without the need for fractionation. As evidenced by 1 H NMR, 13 C NMR, size exclusion chromatography, and matrix assisted laser desorption ionization time-of-flight (MALDI-TOF) mass spectrometry, the fullerene polymers thus obtained possess well-defined structure, narrow polydispersity (∼1.01 by MALDI-TOF mass spectrometry; ∼1.03 by size exclusion chromatography), and high fullerene functionality (∼100%). They can serve as model compounds for the investigations of polymer structures and dynamics.

4 páginas, 4 figuras, 1 esquema.-- et al., In this communication, we present first results on the dielectric response of various end-functionalized polystyrenes (PS). The functional polymers have been prepared by using a combination of anionic polymerization techniques and hydrosilation chemistry that gives well-defined polymers where the functional group can be placed with flexibility and high precision. The data show that for rather large functional groups, the overall polymer matrix properties are altered giving rise to a decrease in the glass transition temperature. The trend can be rationalized in terms of free volume effects caused by the bulky functional groups. However, for cyano-functionalized PS, i.e. PS with a CN group at the chain end, the inclusion of the group does not affect the matrix properties. We show that by taking advantage of the strong dipole moment of the CN group, we can obtain a strong dielectric signal that can be used to selectively study the specific dynamics where the group is located. In other words, by appropriately attaching cyano groups at different part of the chains, these can be used as dielectric probes that allow specific contributions to the alpha relaxation.

A poly(ethylene oxide)-b-polystyrene (PEO-b-PS) diblock copolymer with a number average molecular weight of PEO blocks, M n PEO =8.8 kg/mol, and a number average molecular weight of PS blocks, M n PS =24.5 kg/mol, (volume fraction of the PEO blocks, fPEO, was 0.26) exhibited a hexagonal cylinder (HC) phase structure. Small angle X-ray scattering results showed that the PEO cylinder diameter was 13.3 nm, and the hexagonal lattice was a=25.1 nm. The cylinder diameter of this HC phase structure was virtually the same as that in the blend system constructed by a PEO-b-PS diblock copolymer ( M n PEO =8.7 kg/mol and M n PS =9.2 kg/mol) and a PS homo-polymer ( M n PS =4.6 kg/mol) in which the fPEO was 0.32. The cylinder diameter in this blend sample was 13.7 nm and the hexagonal lattice was a=23.1 nm. Comparing crystal orientation and crystallization behaviors of this PEO-b-PS copolymer with the blend, it was found that the crystal orientation change with respect to crystallization temperature was almost identical. This is attributed to the fact that in both cases the PEO block tethering densities and confinement sizes are very similar. This indicates that when the M n PS of PS homo-polymer is lower than the PS blocks, the PS homo-polymer is located inside of the PS matrix rather than at the interface between the PEO and PS in the HC phase structure. On the other hand, a substantial difference of crystallization behaviors was observed between these two samples. The PEO-b-PS copolymer exhibited much more retarded crystallization kinetics than that of the blend. Based on the small angle X-ray scattering results, it was found that in the blend sample, the HC phase structure was not as regularly ordered as that in the PEO-b-PS copolymer, and thus, the HC phase structure contained more defects in the blend. This led to a suggestion that the primary nucleation process in the confined crystallization is a defect-controlled process. The mean crystallite sizes were estimated by the Scherer equation, and the PEO crystal sizes are on the scale of the confined size.

Matrix-assisted laser desorption ionization (MALDI) time-of-flight (TOF) mass spectrometry (MS) is applied to examine the products arising upon the preparation of chain-end functional polymers via living anionic polymerization techniques. Both post-polymerization functionalizations as well as the use of functionalized initiators are investigated. MALDI-TOF MS is shown to be a sensitive probe for the qualitative analysis of the major and minor oligomers from novel functionalization reactions whose mechanisms are not yet well established. The method is particularly valuable for the identification of the end groups of the minor, and often unexpected, distributions that may be undetectable by other analytical means. Complete characterization of all oligomers generated during functionalization reactions provides an essential tool to the synthetic chemist for understanding the corresponding mechanisms. This insight is necessary for selecting alternative routes or making modifications to the reaction conditions. It is demonstrated that MALDI-TOF MS can convey quantitative information about the yields of the chain-end groups introduced during functionalization. From the cases presented it is evident that post-polymerization reactions allow for better control of chain-end functionality and molecular weight than functionalization with the limited number of currently available protected functionalized initiators.

Oligomerization of ethylene oxide during the functionalization of poly(butadienyl)lithium in benzene and cyclohexane at 25 °C has been investigated by MALDI-TOF MS and 1H NMR. Chemically significant amounts of oligomer were found using 4 equiv. of ethylene oxide ([EO]/[PLi]) after 12 h in both benzene and cyclohexane. No oligomer was observed when the reaction time was minimized.

Phase morphological effect on crystallization kinetics in various nanoconfined spaces in a polystyrene-block-poly(ethylene oxide) (PS-b-PEO) diblock copolymer with a PEO volume fraction of 37 vol% was investigated. The phase morphology was characterized by small-angle X-ray scattering and transmission electron microscopy techniques. When the sample was cast from chloroform solution and annealed at 150 °C, a double gyroid (DG) phase was obtained. After it was subjected to a large-amplitude reciprocating shear, the sample transformed to an oriented hexagonal cylinder (Hex) phase. To obtain a lamellar confined geometry, lamellar single crystals were grown from dilute solutions. The crystallization in the lamellar (Lam) phase was one-dimensionally (1D) confined, while it was two-dimensionally (2D) confined in the DG and Hex phases, although they had different structures. Differential scanning calorimetry (DSC) was employed to study the crystallization kinetics using the Avrami analysis for these three nanoconfined geometries. Heterogeneous nucleation was found in all three samples in the crystallization temperature (Tc) regions studied. DSC results indicated that the crystallization kinetics in the Lam phase was the fastest, and the PEO crystals possessed higher thermodynamic stability than in the DG and Hex phases. For the crystallization kinetics in two 2D-confined phases, at low Tc ( 35 °C) the PEO crystallization was slower in the DG phase than in the Hex phase. The Avrami exponent n-values for the DG and the Hex samples were similar (∼1.8), yet the values of lnK in the DG phase were smaller than those in the Hex phase. This suggested that the linear growth rate was slower in the DG phase than in the Hex phase due to continuous curved channels in the DG phase.

An array of well-defined 4-, 8-, and 12-arm, chain-end functionalized, star polymers and their deuterated analogs has been synthesized using a t-butyldimethylsiloxy-functionalized alkyllithium initiator and anionic polymerization. The design of the synthesis provides for unusually well-defined comparisons of the behavior of the polymers with different chain-end functionality. For each star architecture three polybutadiene polymers were synthesized with the same labeling, the same well-defined degree of branching and molecular weight, but different chain end functionality. Deprotection of the t-butyldimethylsiloxypropyl chain ends of the stars as first synthesized provided stars with hydroxypropyl chain ends. The hydroxypropyl chain ends were further converted to trifluoroethanesulfonyloxypropyl chain ends by tresylation with 2,2,2-trifluoroethanesulfonyl chloride. Measurements of intrinsic viscosities for the hydrogenous and deuterated linear PBs made in the course of characterizing the star functionalities confirm that the dimensions of the linear chains are not affected by isotopic substitution.

A lamellae-forming poly(ethylene oxide)-b-polystyrene (EOS) has been blended with a polystyrene homopolymer (PS) and a PS oligomer (PSO), respectively, to obtain miscible polymer blends (denoted as EOS/PS-32 and EOS/PSO-32, respectively). Both blends exhibit cylindrical microphase morphologies, with the PEO volume fractions being 0.32. The order–disorder transition temperatures (TODT) of both blends are 175 and 84°C, respectively, as determined by temperature-dependent small angle X-ray scattering experiments. The glass transition temperature of the PS matrix (TgPS) for the EOS/PS-32 blend is 64°C as determined by differential scanning calorimetry (DSC), while that for the EOS/PSO-32 blend is only 16°C. Thus, by controlling the crystallization temperatures (TcPEO), two kinds of nano-confined PEO crystallizations have been achieved in these blends: when TODT≫TgPS>TcPEO in the EOS/PS-32 blend, the PEO-block crystallization is confined under a hard PS confinement, while for TODT>TcPEO≳TgPS in the EOS/PSO-32 blend, the PEO-block crystallization is confined under a soft PS confinement. DSC and wide-angle X-ray experiments show that the crystallizations of the PEO blocks in these two confinement environments behave differently. The PEO-block crystallization kinetics in the hard confinement is much slower than that in the soft confinement. The DSC kinetics studies show that for Tc

Heats of interaction of Lewis bases with hexameric and tetrameric alkyllithiums in hydrocarbon solution at 25° have been determined by high dilution solution calorimetry at low base to lithium atom ratios. The Lewis bases utilized include tetrahydrothiophene, tetrahydrofuran, triethylphosphine, triethylamine, and diethyl ether. The organolithiums investigated were n -butyllithium, ethyllithium, isopropyllithium, trimethylsilylmethyllithium, and t -butyllithium. The basicity order based on initial enthalpies of interaction is independent of the alkyllithium compound. Larger enthalpies of interaction were observed for the tetrameric versus hexameric alkyllithiums with the exception of tetrameric t -butyllithium which does not interact significantly with these bases. The sensitivities of the enthalpies to the steric requirements of the base were probed by comparison of the enthalpies for tetrahydrofuran, 2-methyltetrahydrofuran, and 2,5-dimethyltetrahydrofuran. Base coordination to hexameric n -butyllithium is more sensitive to the steric requirements of the tetrahydrofuran bases than is coordination to tetrameric trimethylsilylmethyllithium or isopropyllithium. These results are interpreted in terms of coordination of tetrahydrofuran bases to the intact hexameric aggregate for n -butyllithium; however, it is concluded that the corresponding interaction with hexameric trimethylsilylmethyllithium leads directly to base-solvated tetramers.

Heats of interaction of tetrahydrofuran, tetrahydrothiophene, triethylamine, and triethylphosphine with solutions of n-butyllithium in hexane have been determined by high dilution solution calorimetry. The relative heats of interaction of these bases are in the order tetrahydrofuran > triethylphosphine ≈ triethylamine > tetrahydrothiophene. These results are interpreted in terms of an acid—base interaction which is dominated by electrostatic effects. The alkyllithium aggregate is characterized as a relatively hard Lewis acid species.