Effect of Symmetry and H‐bond Strength of Hard Segments on the Structure‐Property Relationships of Segmented, Nonchain Extended Polyurethanes and Polyureas

Das, Sudipto; Cox, David F.; Wilkes, Garth L.; Klinedinst, Derek B.; Jonáš, Alexandr; Yılgör, Emel; Beyer, Frederick L.

doi:10.1080/00222340701388805

Cited by 109 publications

(126 citation statements)

References 37 publications

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“…Since the molecular weight of the each hard segment is constant in nonchain extended segmented copolymers, hard segment ratios of these copolymers are determined by the molecular weight of the soft segment oligomers [27,28]. Although the impact of a large number of parameters on the structure-morphology-property behavior of non-chain extended segmented copolymers were studied experimentally [16,17,29], there is no systematic modeling which correlates the molecular structure and intermolecular interactions with the morphology and the macroscopic properties of these systems.…”

Section: Introductionmentioning

confidence: 99%

“…Hard segments mainly consist of urethane, urea, urethaneurea, amide, aramide, imide and aromatic ester groups [8][9][10][11][12][13][14][15]. Due to the presence of bidentate hydrogen bonding and their higher cohesive energy densities, segmented polyureas display better microphase separation and improved mechanical properties when compared with their polyurethane analogues [16,17]. Based on their backbone compositions, hard and soft segment type and content, segmented copolymers display broad range of properties and find diverse applications [11,[18][19][20][21][22][23][24][25][26][27][28][29][30][31][32][33][34][35].…”

Section: Introductionmentioning

confidence: 99%

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Multiscale Modeling of the Morphology and Properties of Segmented Silicone-Urea Copolymers

Yıldırım

Yurtsever

et al. 2011

J Inorg Organomet Polym

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Molecular dynamics and mesoscale dynamics simulation techniques were used to investigate the effect of hydrogen bonding on the microphase separation, morphology and various physicochemical properties of segmented silicone-urea copolymers. Model silicone-urea copolymers investigated were based on the stoichiometric combinations of a,x-aminopropyl terminated polydimethylsiloxane (PDMS) oligomers with number average molecular weights ranging from 700 to 15,000 g/mole and bis(4-isocyanatocyclohexyl)methane (HMDI). Urea hard segment contents of the copolymers, which were determined by the PDMS molecular weight, were in 1.7-34% by weight range. Since no chain extenders were used, urea hard segments in all copolymers were of uniform length. Simulation results clearly demonstrated the presence of very good microphase separation in all silicone-urea copolymers, even for the copolymer with 1.7% by weight hard segment content. Experimentally reported enhanced properties of these materials were shown to stem from strong hydrogen bond interactions which leads to the aggregation of urea hard segments and reinforcement of the PDMS.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Multiscale Modeling of the Morphology and Properties of Segmented Silicone-Urea Copolymers

Yıldırım

Yurtsever

et al. 2011

J Inorg Organomet Polym

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“…[1][2][3][4][5][6][7][8] However, the polyurethanes with monodisperse HSs are difficult to prepare and they lose their mono-disperse distribution upon melting due to transurethane reactions. [4] Mono-disperse HS shows an enhanced thermal stability when constituted of diurethanediurea-diamide since trans-reactions do not change the distribution of these HSs.…”

Section: Introductionmentioning

confidence: 99%

“…In the first step, a prepolymer was synthesized from PPO and excess MDI. The copolymers with ND HS were prepared from this prepolymer and a diamine-diamide based on hexamethylene diamine (6) and terephthalic acid (T), i.e., 6T6 (Figure 1). …”

Section: Introductionmentioning

confidence: 99%

Polyurethanes with Narrow‐ and Polydisperse Hard Segment Distributions

Gaymans

2008

Macro Materials & Eng

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Polyurethanes with narrow‐disperse (ND) and polydisperse (PD) hard segment (HS) distributions were prepared in a two‐step process. First, a poly(propylene oxide) end‐capped with MDI (4,4′methylenebis(phenyl isocyanate) was synthesized. To this prepolymer either a diamine–diamide was added to form ND HSs or a mixture of a diamine–diamide and additional MDI to form PD HSs in the copolymers. The polyurethanes displayed a ribbon‐like crystalline morphology, and it was found that the copolymers with ND HSs were more crystalline, had a higher modulus, a less temperature‐dependant modulus, and a higher melting temperature than their PD counterparts. Overall, the polyurethanes with the narrow‐dispersed HSs displayed superior properties.magnified image

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“…However, the crystallinity of these hard segments in the segmented block copolymers is generally low and a large amount of non-crystallised hard segments is present in the polyether matrix. The crystallisation and the stability of the hard segments are improved when the segments are monodisperse in length [21][22][23][24][25][26][27][28][29][30][31][32][33]. Short monodisperse amide segments crystallise fast and almost completely.…”

Section: Introductionmentioning

confidence: 99%

The tensile properties of poly(ethylene oxide)-based segmented block copolymers in the dry and wet state

Husken

Gaymans

2009

J Mater Sci

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The tensile properties of poly(ethylene oxide)-based segmented block copolymers were studied in the dry and wet state. The hard segments were made up of monodisperse crystallisable tetra-amide segments (T6T6T) comprising terephthalate (T) and hexamethylenediamine (6) groups. The length of the segments making up the soft phase was varied from 600 to 10,000 g/mol. The water absorption of the PEO-based copolymers was found to increase exponentially with the PEO concentration. The modulus and yield strength decreased with water absorption and this effect seemed to be mainly the result of a lowering hard segment content caused by their swelling with water. Upon wetting, the copolymers demonstrated an increased yield strain. Furthermore, the ultimate properties were sensitive to the hard segment content, the molecular weight of the copolymer and whether or not strain-hardening could take place. Upon wetting, the fracture stresses decreased whereas the fracture strains increased. The true fracture stresses of the wet samples were as high as those of the dry samples for reasonable amounts of absorbed water.

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Effect of Symmetry and H‐bond Strength of Hard Segments on the Structure‐Property Relationships of Segmented, Nonchain Extended Polyurethanes and Polyureas

Cited by 109 publications

References 37 publications

Multiscale Modeling of the Morphology and Properties of Segmented Silicone-Urea Copolymers

Multiscale Modeling of the Morphology and Properties of Segmented Silicone-Urea Copolymers

Polyurethanes with Narrow‐ and Polydisperse Hard Segment Distributions

The tensile properties of poly(ethylene oxide)-based segmented block copolymers in the dry and wet state

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