Chemical modification of butyl rubber. II. Structure and properties of poly(ethylene oxide)-grafted butyl rubber

Poly(ethylene oxide)-grafted butyl rubbers (IIR-g-PEOs), which were synthesized from potassium salt of polyethylene glycol monomethyl ether (PEGM) and chlorinated butyl rubber, were found to behave like thermoplastic elastomers. The poly(ethylene oxide) (PEO) content of these amphiphilic polymers was ca. 10 wt %, and their PEO lengths were 750, 2000, and 5000, respectively. The grafted segments of PEO in butyl rubber (IIR) aggregated to form the PEO domains in IIR matrix. At constant PEO content, the longer the PEO segment length, the larger the size and the crystallinity of PEO domains became. This PEO domain worked as a cross-linking site and a reinforcing filler. The degree of swelling in water of IIR-g-PEO film that was prepared from PEGM-5000 was largest, but its emulsification ability was smallest among them. © 1995 John Wiley & Sons, Inc.     

Synthesis and properties of butyl rubber–poly(ethylene oxide) graft copolymers with high PEO content

Butyl rubber‐poly(ethylene oxide) (PEO) graft copolymers with high PEO content (40–83 wt %) were synthesized by the functionalization and activation of the double bond moiety of butyl rubber containing high (7 mol %) isoprene content and subsequent reaction with PEO of different molecular weights from 750 to 5000 g/mol. The properties of these copolymers, along with other butyl rubber‐PEO graft copolymers were studied in films and in aqueous solution. Despite the high PEO content, films of the copolymers were quite stable in water with respect to mass loss and were capable of releasing an encapsulated probe molecule in a manner that was dependent on the PEO content. At high PEO content they were resistant to the adhesion and growth of C2C12 cells. Despite the resistance of films to dissolution, it was possible to prepare nanosized aqueous assemblies via a THF‐water exchange process and the sizes of the assemblies were tuned by their method of preparation. The assemblies were also able to encapsulate a probe molecule and were found to be nontoxic in vitro. Combined, this set of properties makes these new amphiphilic copolymers promising for a wide range of potential applications. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013 , 51, 3383–3394     

Dynamic mechanical properties of chlorinated butyl rubber blends

The binary blends are prepared by chlorinated butyl rubber (CIIR) and 3,9-bis[1,1-dimethyl-2{β-(3-tert-butyl-4-hydroxy-5-methylphenyl)propionyloxy}ethyl]-2, 4, 8,10-tetraoxaspiro[5,5]-undecane (AO-80), which are investigated by dynamic mechanical analysis and thermal analysis. It is shown that CIIR/AO-80 blends clearly exhibit two kinds of relaxations, which are attributed to the relaxation of CIIR-rich matrix and AO-80-rich domains, respectively, and attenuated total reflection (ATR)-FTIR spectrum indicates that the existence of intermolecular hydrogen bonds between AO-80 and CIIR. When AO-80 is replaced by petroleum resins, only one loss peak appears, and the position of it is related to the softening point and the content of the petroleum resin. In order to regulate the damping property of CIIR/petroleum resin blend, the ternary blend of CIIR/petroleum resin/AO-80/is prepared and a second peak appears at higher temperature indicating that a good damping material is obtained.     

Cationic graft copolymerization of styrene onto chlorinated butyl rubber

The graft copolymerization of styrene onto chlorinated butyl rubber (Cl-IIR) with stannic chloride as cationic catalyst was studied in cyclohexane, and the rate of polymerization, per cent grafting and grafting efficiency were obtained. Polymerization was carried out in a sealed tube. The product was precipitated in methanol and dried. The increase in weight of Cl-IIR used was regarded as styrene conversion, and the increase in weight after extraction by boiling acetone as the weight of grafted styrene. Grafting was confirmed by fractional dissolution and infrared spectra. The rate of polymerization of styrene was proportional to concentrations of styrene, Cl-IIR and SnCl₄. The per cent grafting increased with styrene and SnCl₄ concentration, but was constant with Cl-IIR concentration. It also increased with time and with halogen content in the polymer. The addition of a polar solvent such as nitrobenzene greatly promoted the grafting reaction and the per cent grafting was 200%.     

Preparation of high damping elastomer with broad temperature and frequency ranges based on ternary rubber blends

Based on the blends of chlorinated butyl rubber (CIIR), nitrile butadiene rubber (NBR) and chloroprene rubber (CR), a kind of high damping elastomer with broad temperature and frequency ranges is prepared. CIIR/NBR binary blend is prepared to take advantage of the immiscibility and the large difference in cross‐link density of the different phases caused by the curatives and accelerators migration. The dynamic mechanical analysis reveals that the binary blend was immiscible and its loss factor (tanδ) versus temperature curves show two separated and expanded loss peaks when compared with those of pure cured CIIR and NBR. In order to improve its damping properties at room temperature, the third component CR with the polarity between CIIR and NBR was blended into the binary blend. The resulted CIIR/NBR/CR ternary blend has gained effective damping properties (tanδ > 0.3) in the temperature range of ?86.4 to 74.6°C and the frequency range of 10^?2 to more than 10⁹ Hz. Other effects on the damping properties of the ternary rubber were also studied. Copyright © 2013 John Wiley & Sons, Ltd.     

Chemical modification of butyl rubber. III. Butyl rubber with D-maltose derivative as pendant groups

A new type of amphiphilic elastomer was synthesized, which consisted of butyl rubber and a D-maltose derivative as a backbone and side groups, respectively. The synthesis was accomplished by the sequence of the three following reactions: (1) Hydroxyl groups of D-maltonolactone were protected by a trimethylsilyl group. (2) The resulting maltonolactone derivative was subjected to a reaction with chemically modified butyl rubber having pendant amino groups. (3) The protecting trimethylsilyl groups on the maltose residues were removed by treating with tetra-n-butylammonium fluoride. This new amphiphilic elastomer behaved as a thermoplastic elastomer and showed good mechanical properties. The saccharide seg-ments aggregated in the hydrophobic butyl rubber matrix to form a microphase-separated structure, as confirmed by differential scanning calorimetry, transmission electron mi-croscopy, small-angle x-ray scattering, and dynamic mechanical measurements. The ag-gregated saccharide domains are estimated to function both as crosslinking sites and rein-forcing fillers in the rubber matrix. © 1995 John Wiley & Sons, Inc.     

Synthesis of amphiphilic block copolymer by metal‐free ring‐opening oligomerization of glycidyl phenyl ether initiated with tetra‐n‐butylammonium fluoride in the presence of poly(ethylene glycol) monomethyl ether

Metal‐free ring‐opening oligomerization of glycidyl phenyl ether (GPE) initiated with tetra‐n‐butylammonium fluoride (n‐Bu₄NF) (5.0 mol %) was performed in the presence of poly(ethylene glycol) monomethyl ether (PEGM) (5.0, 10, 20 mol %) as a chain transfer agent, by which the resulting polymers having narrow molecular weight distribution (M_w/M_n < 1.2) were obtained in 80–84% yield. Solubility of the obtained polymers in water increased with the increase of amount of PEGM, owing to an increase of number of PEGM‐block‐oligo(GPE) molecules compared to that of oligo(GPE) molecules having FCH₂– group at the initiating end as well as a decrease in degree of oligomerization of oligo(GPE). The PEGM‐block‐oligo(GPE) was isolated by filtration of the polymer aqueous solution, whose number‐average molecular weights determined by NMR spectroscopic analysis were almost consistent to the theoretical values. The PEGM‐block‐oligo(GPE) formed micelles in aqueous media, whose average particle diameter was 58 and 140 nm for the copolymers having a composition of PEGM:GPE = 62:38 and 53:47, respectively. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013, 51, 4451–4458     

ATRP of butyl acrylates from functionalized carbon black surfaces

The functionalization of carbon black surface with atom transfer radical polymerization (ATRP) initiating sites and subsequent ATRP of n‐butyl acrylate (n‐BA) and t‐butyl acrylate (t‐BA) from the surface of carbon black is reported. The polymerizations were carried out using CuBr/N,N,N′,N″,N″‐pentamethyldiethylenetriamine as the primary catalytic system in anisole at 70 °C. The initiator density on carbon black surface was tuned and the effect of initiator density on the polymers grafted on the surface was illustrated. Polymerizations were also performed in the presence of a sacrificial initiator to indirectly monitor the molecular weight evolution of polymers formed in the system. Block copolymerization of t‐BA initiated from poly(n‐BA) grafted carbon black was conducted to achieve water‐dispersible carbon black composites after cleavage of the t‐butyl groups. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 4695–4709, 2005     

Synthesis,characterization, and photopolymerization of (meth)acrylate-functional polyisobutylene macromers produced by cleavage/alkylation of butyl rubber

Linear, multi-functional polyisobutylene (PIB) macromers bearing pendent and terminal (meth)acrylate moieties were prepared via electrophilic cleavage/alkylation of butyl rubber in the presence of (3-bromopropoxy)benzene, followed by displacement of the resulting bromide moieties with potassium (meth)acrylate. Number average functionality (F_n) ranged from 2.8–7.9; functional equivalent weights ranged from 2.3–4.7 kg/mol. For comparison, a three-arm, end-functional PIB triacrylate with equivalent weight of 3.3 kg/mol was also synthesized via living polymerization and end quenching with 4-phenoxy-1-butyl acrylate. All polymers were photocured using Darocur 1173 photoinitiator, and curing kinetics were monitored by real time Fourier-transform infrared spectroscopy. All systems reached ~100% conversion by 1,800 s, but the linear macromers displayed slower curing rates compared to the PIB triacrylate. The curing rate of linear macromers increased as molecular weight decreased. Cured networks were characterized using dynamic mechanical analysis and tensile testing. Tensile strength varied from 0.15–0.80 MPa. Young's modulus varied from 0.13–1.8 MPa. Strain at break for most networks ranged from 34–54%, but the network derived from the lowest molecular weight PIB reached 113% at failure. Percent extractables, measured using solvent extraction, was about 2% for linear macromers and about 4% for PIB triacrylate.     

A critical review on analytical methods and characterization of butyl and bromobutyl rubber

The molecular structure characterization of butyl and bromobutyl rubber (BIIR) requires the definition of three main parameters: (I) the unsaturation degree of the rubbers, (II) the total bromine content of the BIIRs, and (III) the functional bromine content of the BIIRs. The analytical methods for the determination of the previously mentioned parameters have been described and critically examined in this review.     

Rubber networks containing unattached macromolecules. I. Linear viscoelastic properties of the system butyl rubber–polyisobutylene

Mixtures of butyl rubber with polyisobutylene (molecular weights 0.055 and 2.3 × 10⁶) up to 50% by weight were crosslinked by sulfur, leaving the polyisobutylene molecules free to reptate in the butyl rubber network. Linear viscoelastic properties were measured in shear creep for periods up to 5 × 10⁵ sec at 25°C and oscillating shear deformations from 0.1 to 3 Hz, at temperatures from 2 to 63°C. Comparison with the properties of a butyl rubber crosslinked without polyisobutylene showed contributions to creep and mechanical loss attributable to the reptating species. Comparison with the properties of polyisobutylene (higher molecular weight) showed that the relaxation times associated with the reptating species in the upper part of the terminal zone are the same for different polyisobutylene contents (25% and 50%) and for 100% polyisobutylene in which no permanent network is present; their contributions to modulus appear to be proportional to the volume fraction of polyisobutylene to a power of about 2/3. The time required in stress relaxation for the portion of the modulus attributable to the reptating species to decay to half its plateau value is, based on the two molecular weights employed, proportional to the polyisobutylene molecular weight to the third power. The magnitude of the associated mechanical loss and its location on the frequency scale can thus be controlled independently.     

Grafting polyacrylates on natural rubber latex by miniemulsion polymerization

Grafting reactions between different acrylates (methyl, ethyl, butyl, hexyl, and lauryl) and natural rubber latex (NRL) were performed in miniemulsion. It is observed that polyacrylates with longer alkyl chain length, i.e., ≥4 carbons, only produce stable dispersions with the hydrophobic azo initiator 2,2′-azobis(2-methylbutyronitrile) (V59). Increasing the reaction temperature from 5 to 72 °C with different initiating systems increases the gel content of the butyl acrylate (BA)-modified NRL. Solid-state ¹H MAS NMR was employed to accurately calculate the grafting efficiency of polyacrylate-modified NRL. Initiating systems such as 2,2′-azobis(4-methoxy-2.4-dimethyl valeronitrile) (V70) and cumene hydroperoxide yield the maximum grafting of ∼53 wt.% efficiency of BA (compared to the BA used) on NRL whereas an enzyme initiator yields the lowest grafting efficiency of 18.3 wt.%. The reaction with V59 as initiator shows the intermediate grafting efficiency of 37 wt.%. Increasing the BA amount from 16.4 to 26.6 wt.% increases the gel content to 47 and 68 wt.%, respectively. The grafting efficiency of BA on NRL is constant at ∼35 wt.% for BA contents from 16.4 to 22.7 wt.%, but for further increasing BA amount to 27 wt.%, a 3.7 times higher grafting efficiency of BA on NRL was observed compared to the other two lower concentrations of BA. Film-forming properties and DSC analysis were used to investigate the phase behavior of polyacrylate-blended and grafted NRL materials; transmission electron microscopy was used to investigate the morphology of BA-grafted NRL.     

Effect of calcium carbonate on the properties of noncuring sealants based on butyl rubber and thermoplastics

The effect of the content, dispersity, and surface polarity of calcium carbonate on the physicomechanical and rheological properties of filled noncuring hot melt sealant formulations based on butyl rubber and various thermoplastics was examined. In the formulations based on nonpolar polymers, the cohesion strength and viscosity increase with an increase in the content and dispersity of calcium carbonate, with the strongest reinforcing effect observed with hydrophobized grades of calcium carbonate. With an increase in the polarity of the polymer base, untreated natural carbonate (chalk) becomes more efficient.     

Radiation Crosslinking of Chlorinated Poly(Isobutylene-co-Isoprene) with Polyfunctional Monomers

Abstract

It is well known that poly(isobutylene-co-isoprene) (butyl rubber, IIR) is degraded by irradiation. However, we demonstrated that IIR, after chlorination (CIIR) crosslinks by electron beam (EB) irradiation. The gel dose for CIIR was 3.8 kGy. To avoid scission of the main chain, various polyfunctional monomers were added for crosslinking of CIIR at lower doses. It was found that trimethylolpropane trimethacrylate (TMPT) is the most effective accelerator for crosslinking of CIIR at a lower dose. The tensile strength of EB crosslinked by CIIR increases almost linearly with increasing TMPT content.     

Investigation of the oxidative cleavage of butyl rubber by selective catalysis

Selective oxidizing cleavage of carbon-carbon double bonds of unsaturated polymers leads to bifunctional oligomers. It is shown, using ruthenium tetroxide in catalytic amount in conjunction with a peracid as co-oxidizing agent, that efficient cleavage of butyl rubber double bonds can be obtained without side reaction. The procedure can be used for analytical as well as for synthetic purpose.     

Study of the ceric ion behavior on the initiation of butyl acrylate polymerization onto amylose

A study of the Ce(IV) ion consumption during graft polymerization of butyl acrylate with amylose was carried out. The Ce(IV) consumed was ca. 80% and the ratio of Ce(IV) to anhydroglucose units was 1/15. Poly(butyl acrylate) (PBA) chains were isolated from the grafted copolymer by the perchloric acid hydrolysis method. The molecular distribution was obtained by gel permeation chromatography (GPC). The number-average molecular weight (M_n) of the grafted chains was 276,000 and the weight-average molecular weight (M_w) was 1,320,000. The total number of grafted chains (mmol) ranged from 0.4410^?3 to 8.710^?3 (amylose from 0.08 g to 1.23 g). Frequency of grafting ranged from 1042 to 704.     

Well-Defined Poly(butyl cyanoacrylate) Nanoparticles via Miniemulsion Polymerization

Summary: Despite the high reactivity of the monomer, nanoparticles with a hydrophobic core based on poly(butyl cyanoacrylate) and a hydrophilic shell based on poly(ethylene oxide) PEO were synthesized in one step by miniemulsion polymerization. Colloidal properties of the nanoparticles were controlled by the structure and the amount of amphiphilic polymer in the aqueous phase, while the molecular weight of core depended on pH of the continuous phase and the polymerization mechanism (anionic or radical). The evolution of the molecular weight of the synthesized poly(butyl cyanoacrylate) was followed as a function of time at pH 7.4 by size exclusion chromatography. As expected, the degradation kinetics depended on the polymerization mechanism. Finally, a model compound, pyrene, was encapsulated in the synthesized nanoparticles. Its release was found to depend on the conditions of nanoparticles synthesis, especially on the polymerization mechanism.     

Atom transfer radical polymerization of n‐butyl methacrylate in an aqueous dispersed system: A miniemulsion approach

Ultrasonication was applied in combination with a hydrophobe for the copper‐mediated atom transfer radical polymerization of n‐butyl methacrylate in an aqueous dispersed system. A controlled polymerization was successfully achieved, as demonstrated by a linear correlation between the molecular weights and the monomer conversion. The polydispersities of the polymers were small (weight‐average molecular weight/number‐average molecular weight < 1.5). The influence of several factors, including ultrasonication, the amount of the surfactant, and the nature of the initiator, on the polymerization kinetics, molecular weight, and particle size was studied. The polymerization rate and molecular weights were independent of the number of particles and only depended on the atom transfer equilibrium. The final particle size, however, was a function of all the parameters. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 4724–4734, 2000     

Synergistic effect of 4,4′‐bis(maleimido) diphenylmethane and zinc oxide on the vulcanization behavior and thermo‐mechanical properties of chlorinated isobutylene–isoprene rubber

It is well known that the vulcanization of chlorinated isobutylene–isoprene rubber (CIIR) with ZnO alone is very slow and the resulting vulcanizate shows low crosslinking density as well as poor mechanical and thermal properties. For these problems to be addressed, 4,4′‐bis(maleimido) diphenylmethane (BMDM) has been applied along with ZnO to cure CIIR. The curing behavior was investigated using oscillating disk rheometer and differential scanning calorimetry analysis. The crosslinking densities, mechanical, dynamic mechanical, and thermal properties of the vulcanizates were also evaluated as a function of BMDM content. From the rheometer and differential scanning calorimetry analysis, it has been confirmed that the rate of curing, as well as the extent of curing between CIIR and ZnO, has remarkably increased in the presence of BMDM. The Diels–Alder reaction between the in situ formed conjugated diene butyl from CIIR/ZnO with the maleic moieties of BMDM has been identified as a primary reason for the higher rate and state of cure. The crosslinking densities of the vulcanizate CIIR/ZnO have significantly increased with increase in the content of BMDM. As a result, the compression set of the vulcanizate was remarkably decreased at elevated temperature. Moreover, the vulcanizates contain BMDM that has exhibited high thermal degradation temperature and good retention of the mechanical properties even after 7 days of thermal ageing. Copyright © 2016 John Wiley & Sons, Ltd.     

Structure and rheology of hyperbranched and dendritic polymers. II. Effects of blending acetylated and hydroxy‐terminated poly(propyleneimine) dendrimers with aqueous poly(ethylene oxide) solutions

The effect of adding acetylated poly(propyleneimine) dendrimers to the structure and rheology of aqueous solutions of high molecular weight poly(ethylene oxide) (PEO) was investigated by rheology and small‐angle neutron scattering in a temperature range of 10–40 °C. In the semidilute regime, the steady shear rheology of PEO solutions was unmodified by the addition of dendrimers at a comparable weight concentration. At the highest concentrations studied, the addition of acetylated dendrimers suppressed the onset of a low‐frequency elastic modulus at the lowest temperature investigated. For comparison, the addition of PEO of a comparable molecular weight at the same weight fraction resulted in a milder suppression but, unlike the dendrimers, greatly increased the solution viscosity. The addition of acetylated dendrimers to a semidilute PEO solution at 10 °C substantially reduced the solution turbidity. These effects on the rheology and optical properties were confirmed by small‐angle neutron scattering measurements of the molecular structure of the mixture. Additional SANS measurements in the dilute regime (0.1 wt % PEO) showed quantitatively that the dendrimers decorated the PEO chains in a necklace structure, such as that observed previously for micelles. The results suggested a mechanism of rheology modification whereby the dendrimers disrupted the association network structure in the PEO solution at lower temperatures by preferentially associating with the PEO chains in solution. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 38: 874–882, 2000