Abstract:This paper is a review of the alkyllithium system for the copolymerization of butadiene and styrene. The alkyllithium system offers a very versatile tool by which a wide variety of styrene butadiene copolymers can be made to fit a particular application. Included are discussions of block and non-block copolymers of styrene butadiene, copolymers with functional groups, and copolymers with varying microstructure. I n addition, wear and traction data on a series of styrene butadiene copolymers with varying styren… Show more
“…The goal of this work is to determine if systematically varying the comonomer transition region in the tapered block or inverse tapered block copolymers at the molecular chain level controls the resultant morphology and macroscopic physical properties. Styrene and butadiene comonomers were chosen as they are known to yield immiscible copolymer diblocks which phase separate, , thereby providing a reference case for comparison to new tailored structures. Previously, Epps and co-workers have demonstrated that styrene–isoprene copolymers can adopt double-gyroid morphologies, with reductions in order–disorder temperatures for tapered block copolymers relative to discrete block copolymers .…”
Systematic variation of comonomer concentration in individual polymer chains is responsible for unique phase behaviors in different types of copolymers. Controlled self-assembly of gradient copolymers into desired morphologies is theoretically understood but practically challenging, and identifying heterogeneous phase partitioning of individual comonomers in those resulting morphological regions can be difficult. Building on previous work where improved methods were used to elucidate heterogeneous comonomer partitioning in styrene−butadiene gradient copolymers [Clough et al. Macromolecules 2014, 47, 2625, the arrangement of the styrene and butadiene monomers in only a fraction of the total chain length is used here to significantly perturb the overall morphology and physical properties of copolymers. Importantly, the chemical composition of all copolymers was held nearly fixed in this study. The resulting tapered and inverse tapered block copolymers contain nanometer length scale interfaces that differ from one another and differ dramatically from that observed in a control block copolymer composed of chains with a discrete interface. Evidence is presented that butadiene can reside in rigid environments, styrene can reside in mobile environments, and their relative amounts can be varied based on the gradient design. The connection between the molecular design of the gradient, the resulting nanometer-length scale interfacial structures, and mechanical properties is demonstrated using a combination of variable temperature solid-state NMR, modulated DSC (differential scanning calorimetry), AFM (atomic force microscopy), and rheology experiments.
“…The goal of this work is to determine if systematically varying the comonomer transition region in the tapered block or inverse tapered block copolymers at the molecular chain level controls the resultant morphology and macroscopic physical properties. Styrene and butadiene comonomers were chosen as they are known to yield immiscible copolymer diblocks which phase separate, , thereby providing a reference case for comparison to new tailored structures. Previously, Epps and co-workers have demonstrated that styrene–isoprene copolymers can adopt double-gyroid morphologies, with reductions in order–disorder temperatures for tapered block copolymers relative to discrete block copolymers .…”
Systematic variation of comonomer concentration in individual polymer chains is responsible for unique phase behaviors in different types of copolymers. Controlled self-assembly of gradient copolymers into desired morphologies is theoretically understood but practically challenging, and identifying heterogeneous phase partitioning of individual comonomers in those resulting morphological regions can be difficult. Building on previous work where improved methods were used to elucidate heterogeneous comonomer partitioning in styrene−butadiene gradient copolymers [Clough et al. Macromolecules 2014, 47, 2625, the arrangement of the styrene and butadiene monomers in only a fraction of the total chain length is used here to significantly perturb the overall morphology and physical properties of copolymers. Importantly, the chemical composition of all copolymers was held nearly fixed in this study. The resulting tapered and inverse tapered block copolymers contain nanometer length scale interfaces that differ from one another and differ dramatically from that observed in a control block copolymer composed of chains with a discrete interface. Evidence is presented that butadiene can reside in rigid environments, styrene can reside in mobile environments, and their relative amounts can be varied based on the gradient design. The connection between the molecular design of the gradient, the resulting nanometer-length scale interfacial structures, and mechanical properties is demonstrated using a combination of variable temperature solid-state NMR, modulated DSC (differential scanning calorimetry), AFM (atomic force microscopy), and rheology experiments.
“…If both monomers are loaded simultaneously and “living” anionic polymerization is conducted in one stage, the copolymer prepared will in many cases have a gradient composition profile along the chain (see Figure c,d). Experimental verification of this fact has been repeatedly reported in the literature. − 1 Examples of the shape of the polymer composition ( X A ( p )) vs the conversion ( p ) for some binary systems: (a) homogeneous copolymer; (b) ideal block copolymer; (c) styrene/butadiene in toluene with lithium counterion ( r 1 = 0.004, r 2 = 12.9); (d) styrene/butadiene in toluene with sodium counterion ( r 1 = 0.42, r 2 = 0.30) …”
Section: Introductionmentioning
confidence: 73%
“…Experimental verification of this fact has been repeatedly reported in the literature. [8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23] Binary anionic copolymerization of styrene with diene monomer (butadiene or isoprene) in the presence of an initiator based on alkali metal is likely to be the most thoroughly investigated. For instance, in the organolithium-initiated copolymerization of isoprene and styrene in hydrocarbon solvents, isoprene is generally polymerized almost exclusively at the first stage of the process, followed by polymerization of styrene to give a terminal polystyrene block.…”
Section: Introductionmentioning
confidence: 99%
“…[8][9][10][11][12][13] An analogous situation occurs when isoprene is replaced by butadiene. [14][15][16][17][18][19][20][21][22][23] The products formed for such a process at complete conver-sion of monomers are so-called tapered block copolymers (TBC). 13,14,23,24 These macromolecules differ from those of ideal block copolymers (IBC) by two features.…”
Section: Introductionmentioning
confidence: 99%
“…The reactivity ratios are influenced to no lesser extent by the presence in the reaction system of polar substances like ethers or amines. 13,14,17,[19][20][21][22][23] So, the addition to benzene or cyclohexane of even a trace amount of tetrahydrofuran can be responsible for a dramatic change in the primary structure of the macromolecules formed. Namely, it results in a strong increase of the intramolecular mixing of different type monomer units along the copolymer chains, i.e., to an increase of their "taper" character.…”
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This paper is a report of methods of balancing wear and traction in passenger tire treads with lithium catalyzed polymers. The results demonstrate the versatility of the alkyllithium system for preparing a wide variety of polymers and copolymers with differing wear and traction properties in passenger tire treads. In addition, the use of this system for preparing polymers with improved processing and green strength is briefly discussed.
ZUSAMMENFASSUNG :Es wird iiber den Ausgleich von VerschleiB und Rutschverhalten bei Personenwagenreifen mit Lithium-katalysierten Polymeren berichtet. Die Ergebnisse zeigen die Vielfaltigkeit von Alkyllithium-Systemen zur Herstellung einer breiten Palette von Polymeren und Copolymeren mit verschiedenen VerschleiB-und Abriebeigenschaften. Ferner wird die Anwendung dieses Systems fiir die Herstellung von Polymeren mit verbesserter Verarbeitbarkeit und Festigkeit diskutiert.In a previous paperl, we demonstrated the versatility of the alkyllithium system for preparing butadienelstyrene copolymers with a wide variety of propert,ies and applications. I n addition, we demonstrated a relationship between tread wear and traction properties in passenger tires constructed from butadiene/styrene copolymers with varying styrene content and varying microstructure. We showed that as the styrene content or vinyl content was increased in the polymers, a corresponding increase in T, (glass transition temperature) resulted. Also, the compounded stocks from these polymers exhibit,ed an increase in the YMI** with increasing vinyl or styrene content. The wear resistance properties of tires were shown t o decrease with increasing * Paper presented a t the meeting of the GDCh-Fachgruppe "Makromoleku-* * Temperature where YOUNG'S Modulus Index reaches 10000 lbs./sq.in. -ASTM lare Chemie" in Bad Nauheim, Germany, March 21, 1972. 797-64.
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