Star-block polymers of multiple polystyrene-b-polyisobutylene arms radiating from a polydivinylbenzene core

Asthana, Siddhartha; Kennedy, Joseph P.

doi:10.1002/(sici)1099-0518(19990701)37:13<2235::aid-pola38>3.0.co;2-v

“…The simplest and most common branched architecture is a star block copolymer comprising A–B arms with the B ends connected to a central core (denoted (A–B) n , where n is the number of arms). Star block copolymers with glassy end blocks, often referred to as “radial” block copolymers in the context of TPEs, have been prepared by a variety of methods. − Commercially, star block copolymers are preferred in some applications where the block copolymer is blended with other components such as in thermoplastic toughening, pressure-sensitive adhesives, and asphalt modification . In many instances neat star block copolymers with glassy end blocks have been found to exhibit higher ultimate strength (σ u ) than their linear analogues, ,,− which commonly comes at the expense of reduced breaking strains (ε b ). ,,,, In instances where direct comparisons between linear and star block copolymer have been made, reports of both enhanced and diminished strain recovery (with respect to the corresponding linear polymers) can be found in the literature.…”

Section: Introductionmentioning

confidence: 99%

“…Star block copolymers with glassy end blocks, often referred to as “radial” block copolymers in the context of TPEs, have been prepared by a variety of methods. − Commercially, star block copolymers are preferred in some applications where the block copolymer is blended with other components such as in thermoplastic toughening, pressure-sensitive adhesives, and asphalt modification . In many instances neat star block copolymers with glassy end blocks have been found to exhibit higher ultimate strength (σ u ) than their linear analogues, ,,− which commonly comes at the expense of reduced breaking strains (ε b ). ,,,, In instances where direct comparisons between linear and star block copolymer have been made, reports of both enhanced and diminished strain recovery (with respect to the corresponding linear polymers) can be found in the literature. Semicrystalline TPEs with well-defined branched architectures have not been studied in detail, but some evidence of improved recovery can nonetheless be found. , Improvements in the mechanical properties in branched TPEs have been attributed to increased connectivity between the rubbery phase and the hard domains, which is better able to distribute stresses through the network. , Moreover, the processability was found to depend primarily on the composition and molecular weight of the arms and only weakly on n for n ≥ 3. − …”

Section: Introductionmentioning

confidence: 99%

“…In some cases, the contribution of the covalent cross-links is obscured by changes in the morphology arising from the architectural change, broad molecular weight (arm number) distributions, ,, and non-negligible filler effects from the core of the star. ,, Here we attempt to avoid contributions from morphological changes and linking chemistry to better understand the influence of the branch point on the mechanical response. To this end, we focus on precisely defined 6-arm star block polymers prepared by anionic polymerization, chlorosilane coupling, and catalytic hydrogenation .…”

Section: Introductionmentioning

confidence: 99%

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Mechanical Properties of Star Block Polymer Thermoplastic Elastomers with Glassy and Crystalline End Blocks

Burns

¹

,

Register

²

2016

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The mechanical properties of thermoplastic elastomers (TPEs) consisting of 6-arm star block polymers with glassy, crystalline, or composite crystalline–glassy physical cross-linking (hard) domains were investigated and compared to the analogous linear triblock or pentablock polymers. The 6-arm stars exhibited qualitatively similar solid-state morphologies and phase behavior to their linear counterparts, as demonstrated by small-angle X-ray scattering and differential scanning calorimetry. Consequently, the architecture had minimal impact on the small-strain behavior in uniaxial extension at room temperature. As the applied strain increased, the star polymers exhibited more pronounced strain hardening than the corresponding linear TPEs, resulting in an increase in the ultimate strength of 20% for the polymers with crystalline end blocks and 30% when the end blocks were glassy. Each of the three star polymers exhibited superior recovery (i.e., lower residual strain) and lower hysteresis than the corresponding linear TPEs when subjected to repeated strain cycles. The enhancement in the recovery was most significant for the polymers with glassy hard domains. The TPEs with crystalline or crystalline–glassy domains recovered more rapidly than the corresponding linear block polymers but showed only modest improvements in the recovery measured after the specimens were allowed to rest for 5 min. These results indicate that the covalent junction at the core of the star strengthens and accelerates the recovery of the network but does not greatly suppress plastic deformation of the crystallites. Overall, this work demonstrates that the mechanical performance of block polymer TPEs can be improved by using a star macromolecular architecture.

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“…[5,[8][9][10][11] Straightforward processability, high deformability, and optimum level of stiffness, strength, and reversibility are generally the important considerations for the application of block copolymers. [5,[10][11][12] Styrene-based triblock copolymers with asymmetric styrene end blocks are desirable for enhanced toughness and processability.…”

Section: Introductionmentioning

confidence: 99%

“…[5,[8][9][10][11] Straightforward processability, high deformability, and optimum level of stiffness, strength, and reversibility are generally the important considerations for the application of block copolymers. [5,[10][11][12] Styrene-based triblock copolymers with asymmetric styrene end blocks are desirable for enhanced toughness and processability. [12] There is much theoretical [13,[15][16][17][18] and experimental evidence [5,6,12,14,19,20] confirming a significant shift in the block copolymer phase diagram introduced by architectural modification.…”

Section: Introductionmentioning

confidence: 99%

Correlation between Molecular Architecture, Morphology, and Deformation Behaviour of Styrene/Butadiene Block Copolymers

Adhikari

¹

,

Michler

²

,

Huy

³

et al. 2003

Macro Chemistry & Physics

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The correlation between the molecular architecture, morphology, and micromechanical deformation behaviour of styrene/butadiene (SB) block copolymers with different architectures (linear and star block copolymers, total styrene content, ΦST = 0.74) was studied using dynamic mechanical analysis (DMA), uniaxial tensile testing, scanning force microscopy (SFM), and high voltage electron microscopy (HVEM). Deformation of the individual phases under uniaxial strain at the molecular level was monitored by Fourier transform infrared (FT‐IR) spectroscopy. It was demonstrated that the morphology and deformation behaviour of these block copolymers are strongly influenced by their molecular topology, block symmetry, and the nature of the interface between the component blocks. While the cylindrical morphology (hexagonal polybutadiene (PB) cylinders in polystyrene (PS) matrix) was observed in a symmetric SBS triblock copolymer with ΦST = 0.74, a “two‐component three‐phase” morphology was found in an asymmetric star block copolymer having an equivalent chemical composition and an SBS arm structure. Likewise, an SBS triblock copolymer with a composition identical to the former ones but with highly asymmetric PS end blocks revealed a lamellar morphology. While no locally confined deformation zones were observed in the lamellar block copolymers, the cylindrical block copolymer was found to deform through the formation of highly localised craze‐like deformation zones.

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Carbocationic Polymerization*This chapter has already been published in: Matyjaszewski, K., Müller, A. H. E., Controlled and Living Polymerizations, 2009. Copyright Wiley‐VCH Verlag GmbH & Co. KGaA. Reproduced with kind permission of the authors.

De

¹

,

Faust

²

2012

Materials Science and Technology

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The sections in this article are Introduction Mechanistic and Kinetic Details of Living Cationic Polymerization Living Cationic Polymerization Monomers and Initiating Systems Additives in Living Cationic Polymerization Living Cationic Polymerization: Isobutylene ( IB ) β‐Pinene Styrene ( St ) p ‐Methylstyrene ( p ‐ Me St ) p ‐Chlorostyrene ( p ‐ Cl St ) 2,4,6‐Trimethylstyrene ( TMe St ) p ‐Methoxystyrene ( p ‐ Me OSt ) α‐Methylstyrene (α Me St ) Indene N ‐Vinylcarbazol Vinyl Ethers Functional Polymers by Living Cationic Polymerization Functional Initiator Method Functional Terminator Method Telechelic Polymers Macromonomers Synthesis using a Functional Initiator Synthesis using a Functional Capping Agent Chain‐End Modification Block Copolymers Linear Diblock Copolymers Linear Triblock Copolymers Synthesis using Difunctional Initiators Synthesis Using Coupling Agents Block Copolymers with Nonlinear Architecture Synthesis of A n B n Hetero‐Arm Star‐Block Copolymers Synthesis of AA ′ B , ABB ′, and ABC Asymmetric Star‐Block Copolymers using Furan Derivatives Block Copolymers Prepared by the Combination of Different Polymerization Mechanisms Combination of Cationic and Anionic Polymerization Combination of Living Cationic and Anionic Ring‐Opening Polymerization Combination of Living Cationic and Radical Polymerization Branched and Hyperbranched Polymers Surface Initiated Polymerization — Polymer Brushes Conclusions

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Star-block polymers of multiple polystyrene-b-polyisobutylene arms radiating from a polydivinylbenzene core

Cited by 19 publications

References 19 publications

Mechanical Properties of Star Block Polymer Thermoplastic Elastomers with Glassy and Crystalline End Blocks

Mechanical Properties of Star Block Polymer Thermoplastic Elastomers with Glassy and Crystalline End Blocks

Correlation between Molecular Architecture, Morphology, and Deformation Behaviour of Styrene/Butadiene Block Copolymers

Carbocationic Polymerization*This chapter has already been published in: Matyjaszewski, K., Müller, A. H. E., Controlled and Living Polymerizations, 2009. Copyright Wiley‐VCH Verlag GmbH & Co. KGaA. Reproduced with kind permission of the authors.

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