Halogen-free polyisobutylene by in situ methylation of living polyisobutylene using dimethylzinc

Summary Halogen-free polyisobutylene (PIB) was synthesized by in situ methylation of living PIB using dimethylzinc. Quantitative methylation of living PIB was achieved within 60 min using a ratio of [(CH₃)₂Zn]/[TiCl₄]₀= 1 without any side reactions. Under similar conditions, living PIB capped with 1,1-diphenylethylene (PIB-DPE⁺) yielded close to 1:1 mixture of methoxy- and methyl-functionality. By using the ratio of [(CH₃)₂Zn]/[TiCl₄]₀≥ 3, however, quantitative methylation of PIB-DPE⁺ could be achieved in 120 min without any side reactions as confirmed by spectroscopic and chromatographic analyses. Received: 1 February 2000/Revised version: 23 April 2000/Accepted: 23 April 2000     

聚异丁烯丁二酸酐中聚异丁烯的液相色谱分析

利用高效液相色谱,采用外标法测定聚异丁烯丁二酸酐中间产品中聚异丁烯的含量,采用示差检测器进行检测。色谱柱为自制改性氧化铝柱（4.6mm×250mm,15.0μm）,正己烷为流动相,流速为1mL/min。标准曲线相关性良好,聚异丁烯平均线性范围为3.8-111g/L,其线性相关系数为0.9998,相对标准偏差为2.08%,回收率为98.5%-101.5%。该方法简便、经济、结果准确。     

Synthesis of phenol-terminated polyisobutylene: Competitive chain transfer reactions

Polymerization of isobutylene initiated by either aluminum trichloride or tin tetrachloride were conducted in the presence of alkyl phenols in both n-heptane and methylene dichloride solutions at temperatures between ?10 and ?70°C. The resultant polymers contained both unsaturated and phenolic endgroups in varying proportions dependent upon reaction conditions. Increased phenol concentrations in the polymerization medium resulted in decreased polymer molecular weights and increased phenol endgroup content. Increased reaction temperature reduced polymer molecular weights and phenol endgroup content. Chain lengths governed by ring alkylation were found to be less sensitive to polymerization temperature than those determined by other modes of chain transfer.     

Coupling of mutual diffusion to viscoelasticity in moderately concentrated polyisobutylene solutions

The normalized intensity autocorrelation function g⁽²⁾(t) were obtained by dynamic light scattering for moderately concentrated entangled solutions of polyisobutylene in n-heptane at 25.0 °C and in isoamyl isovalerate (IAIV) at 25.0 °C (Θ). The obtained data have been successfully analyzed by the ‘procedure X’ familiar for determination of mechanical relaxation spectra on the basis of the recent theory for g⁽²⁾(t). The results have shown that while the mutual diffusion coefficient D increases in the n-heptane solutions and decreases in the IAIV solutions with increasing polymer mass concentration c, the friction coefficient ζ for both solutions increases with c showing the same power-law behavior irrespective of the weight-average molecular weight M_w and solvent quality. It has been found that the instantaneous longitudinal modulus L₀ for n-heptane solutions increases in proportion to c², obeying the familiar relation for the plateau value (4/3)G_N of the longitudinal stress relaxation modulus, but L₀ for the IAIV solutions becomes progressively smaller than the values predicted from the relation with decreasing c. The terminal relaxation time τ_m has been found to follow the power-law τ_m∝M_w^3.4 established by rheological measurements.     

低相对分子质量聚异丁烯热降解制备遥爪聚异丁烯

高温时将LMPIB[低Mn(数均相对分子质量)聚异丁烯]热降解,用黏数测定产物的Mn,用碘量法测定产物的双键含量,用红外光谱(FT-IR)法和核磁共振碳谱(13C-NMR)法分析产物的分子结构,并研究了反应条件对产物双键官能度的影响。结果表明:当温度≥285℃时,LMPIB降解并生成了不饱和β-末端双键,提高了LMPIB的双键官能度;经315℃反应1.00 h后,产物的双键官能度达到1.57,n(末端α-双键)∶n(末端β-双键)=1∶3,并得到含α-、β-末端双键的遥爪齐聚物与含β-末端双键的齐聚物的混合物,n(遥爪齐聚物)∶n(单官能度齐聚物)≈1∶2。     

Coupling of living polystyryllithium anions and living polyethyl vinyl ether cations

Summary Living polystyryllithium anions and living polyethyl vinyl ether cations have been successfully coupled. Indeed, no residue of any of the two original homopolymers is observed in the final product, when they are used in a stoichiometric amount. This method has been exploited in order to synthesize AB and ABA polyethyl vinyl ether (PEVE) (A)/polystyrene (PSt) (B) block copolymers with a high efficiency.     

Synthesis of star-shaped poly(vinyl ether)s by living cationic polymerization: Pathway for formation of star-shaped polymers via polymer linking reactions

Summary: Star-shaped polymers of isobutyl vinyl ether (IBVE) with a microgel core of an aliphatic divinyl ether (2) were synthesized in high yield on the basis of the living cationic polymerization with the HCl/ZnCl₂ initiating system. GPC analysis demonstrated that linear coupling products ("two-armed" polymers) and three-armed star polymers formed during the early stages of the linking reaction, and that subsequent coupling reactions between such low molecular weight star polymers gave star-shaped polymers with more arms. The number of arms ranged from 5 to 22, which increased with increasing [2]₀/[P^*] ratio and/or shortening the arm chain. Received: 11 April 2000/Accepted: 24 April 2000     

New polyisobutylene starsXI. Synthesis and characterization of allyl-telechelic octa-arm polyisobutylene stars

The synthesis and characterization of a novel star comprising eight allyl-terminated polyisobutylene (PIB) arms radiating from a calix[8]arene core is described. The synthesis was accomplished by a core-first method, by inducing the living polymerization of isobutylene (IB) by a suitably functionalized calix[8]arene initiator (1) in conjunction with BCl₃-TiCl₄ coinitiators, and terminating the growth of the living PIB^⊕ arms by allyltrimethylsilane. The relative concentrations of BCl₃ and TiCl₄ are critical for the synthesis of well-defined 8-arm stars. Characterization of the products (which included triple detector GPC studies and ¹H NMR spectroscopy) indicated quantitative allylation. A mechanism which summarizes the experimental observations is proposed. Received: 17 July 1997/Revised version: 11 September 1997/Accepted: 19 September 1997     

Coupling exothermic and endothermic reactions in adiabatic reactors

The steady state and the dynamic behavior of coupling exothermic and endothermic reactions in directly coupled adiabatic packed bed reactors (DCAR) are analyzed using one-dimensional pseudo-homogeneous plug flow model. Two different configurations of DCAR (simultaneous DCAR—SIMDCAR and sequential DCAR—SEQDCAR) are investigated. In SIMDCAR, the catalyst bed favors both exothermic and endothermic reactions and both reactions occur simultaneously. SEQDCAR has alternating layers of catalyst beds for exothermic and endothermic reactions and hence the exothermic and endothermic reactions occur in a sequential fashion. The performance of both reactors, in terms of conversion achieved and manifested hot spot behavior, is compared with that of the co-current heat exchanger type reactor. Various possible operational regimes in SIMDCAR have been classified and the conditions for the existence of hot spots or cold spots in SIMDCAR are obtained analytically for the first order reactions with equal activation energies. The reactor behavior for the reactions with non-equal activation energies is also presented. The preliminary criteria for the selection of suitable reactor type and the general bounds on the reaction parameters to obtain the desired conversion for endothermic reaction with minimal temperature rise are proposed. The dynamic behavior of these reactors is important for control applications and we have reported some of the transient behavior.     

Silica-grafted polyisobutylene and butyl rubber

Summary Silica surfaces have been modified by reaction with ClSi(CH₃)₂CH₂-CH₂-C₆H₄CH₂Cl (I) and the solids were used in conjunction with Et₂AlCl to initiate the surface-graft polymerization of isobutylene. Experimental conditions have been defined to obtain respectable grafting rates, grafting ratios and grafting efficiencies.     

Multi‐point monitoring of cross‐linking reactions

The feasibility of deploying optical fiber sensors to obtain qualitative and quantitative information on the cross‐linking characteristics of thermosetting resin systems has been demonstrated by a number of researchers. This article is concerned with the demonstration of a low‐cost fiber‐optic Fresnel sensor system for monitoring the cross‐linking reactions at multiple locations. Cross‐linking reactions can be influenced by a number of parameters including the stoichiometry of the resin and hardener, and the heat‐transfer rates in and out of the preform as a function of the cross‐section of the preform. In situations where there is a variation in the thickness of the preform or when large components are processed, a facility to monitor the cross‐linking reactions at multiple locations will be valuable because the rate and extent of the cross‐linking can be inferred. In this article, six Fresnel sensors were immersed in individual vials containing an epoxy/amine resin system and processed (cross‐linked) in an air‐circulating oven. One additional vial with a Fresnel sensor immersed in the neat epoxy resin (no hardener) was co‐located in the oven to enable the effect of temperature to be monitored. The feasibility of using the multiplexed Fresnel sensors for cure monitoring was demonstrated successfully. The sensors in the post‐cross‐linked samples were used to study the effects of heating and cooling cycles. The feasibility of detecting the glass transition temperature using the Fresnel sensor is discussed along with the factors that give rise to variability in the output Fresnel signals. © 2014 The Authors. Journal of Applied Polymer Science Published by Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 41088.     

功能性聚异丁烯

在异丁烯正离子聚合中加入乙烯基于基三甲基氯化胺，该化合物不仅没有破坏聚合体系，而且1H—NMR谱图证实还有部分共聚合进入聚异丁烯，使传统的聚异丁烯带上了亲水性基团，赋予聚异丁烯一定的亲水性。     

二甲基双环氧乙烷环氧化低相对分子质量聚异丁烯

采用过硫酸氢钾复合盐(Oxone)/丙酮体系制备二甲基双环氧乙烷(DMD)环氧化LMPIB(低相对分子质量聚异丁烯)。探讨了反应体系中溶剂、n(Oxone)∶n(NaHCO3)比例、V(H2O)∶V(丙酮)比例、反应温度和反应时间等对产物的双键转化率、环氧值和环氧收率的影响。结果表明:采用单因素试验法优选出DMD环氧化LMPIB的适宜工艺条件是"0~5℃反应0.5 h→25℃反应1.5 h"、n(Oxone)∶n(NaHCO3)=1∶2.40和V(H2O)∶V(丙酮)=5∶4,即反应体系中水150 mL、丙酮120 mL、Oxone和NaHCO3分别为23.05 g和15.12 g;此时,环氧化LMPIB的环氧值0.138 8 mol/100 g、双键转化率62.68%和环氧收率67.10%。     

Synthesis and characterization of polyisobutylene propellant binders

Substantial gains in rocket motor cost-effectiveness or performance can be achieved through improved propellant aging characteristics or better and more reproducible mechanical properties. The approach to achieving these goals is the development of a new binder based on ideal networks formed from polyisobutylene (PIB) prepolymers. PIB has a greater resistance to oxidation than polybutadiene which is used in many current composite systems.The ideal networks are generated through the use of PIB prepolymers with controlled molecular weight distributions and well defined functionality. PIB prepolymers evaluated in this study were synthesized by Dr. J. P. Kennedy at the University of Akron using the inifer process which allows close control of molecular weight distribution, functionality and types of end group. Hydroxy-terminated PIB's with molecular weights that varied from 1500 to 6000 and functionalities of 2 or 3 were synthesized. After a thorough characterization, gumstocks were prepared with isocyanate curatives of controlled functionality. The effects of M_c and plasticizer content on mechanical properties were determined in addition to the aging characteristics of the systems. Accelerated aging studies of the gumstocks were conducted.This work was performed under Contract No. F04611-82-C-0066, AFRPL/MKPA Edwards AFB, CA, Project Manager -Lt. Joseph W Lewis     

Dynamic rheological properties of polyisobutylene

The viscoelastic properties of polyisobutylene melts were investigated as functions of temperature, molecular weight, and molecular weight distribution. The effect of molecular weight distribution was studied through the use of blends of narrow distribution polymers. The Ninomiya and Ferry theory was used successfully to predict the viscosity of the blends. It was observed that the temperature coefficient for flow was independent of molecular weight distribution and of molecular weight. It was shown, at least in the case of polyisobutylene melts, that the temperature dependence of elasticity is less for polymers with greater polydispersity.     

Oxyethylation and carbonation of telechelic polyisobutylene anions

Summary The synthesis of (CH₃)₃C≈PIB≈CH₂ C(=CH₂) CH₂CH₂CH₂OH and (CH₃)₃C≈PIB≈CH₂ (=CH₂) CH₂COOH have been achieved by oxyethylation and carbonation of telechelic polyisobutylene anions: (CH₃)₃C≈PIB≈CH₂C(=CH₂)CH₂⊝. The latter macroanions were prepared from (CH₃)₃C≈PIB≈CH₂C(CH₃)₂Cl by one-pot dehydrochlorination-metalation with n-BuLi/t-BuOK in hexanes. The structure of the products was established by detailed ¹H and ¹³C NMR analyses which also involved the characterization of 4-neopentyl-4-penten-1-ol and 3-neopentyl-3-butenoic acid model compounds.     

Stored elasticity in flowing solutions of polyisobutylene as measured by recoil

Recoil measurements in capillary flow are performed with solutions of polyisobutylene in toluene and used to calculate a shear modulus G. The shear rate dependence of G is explained in terms of a stiffening function and a network destruction function, the first contribution dominating in the measured range. Good agreement is found for recoil in both the capillary and in a rotational viscometer.