{"record":{"author":{"account_ref":null,"orcid":null},"builds_on":[],"content_schema":"pubphys.content.revision/1","content_sha256":"4d64b4c97460d6cf6601abb11ca886058a43c22dba7e611b3e127047dbbb6ec9","created":"2026-10-03T07:17:57Z","files":[],"origin":{"assisted_by":[],"kind":"seed"},"parents":["5475cf5dc5b1a72283d26dc95dc6e00d7ea4e00096a7c6492e409a1816eeb011"],"salt":"9d885cc1eb175a3d1c8766e84b62adfafb248ad5ff64d37d0af6ef3aba22b37d","schema":"pubphys.record/2","site":"pubphys.com","target":null,"type":"revision"},"content":{"answer_type":"mechanism","assisted_by":[],"external_id":"bio.polymer-dynamics.extensional-melt-solution","kind":"phenomenon","literature_status":"contested","n":"1","parents":[],"plain":"When an entangled polymer melt is stretched fast, its resistance to stretching drops, while a solution of the same polymer with the same number of entanglements becomes stiffer. Tube theory predicts the same behaviour for both, and why they differ is disputed.","posed_since":"2003","precise":"In uniaxial extension of monodisperse entangled polystyrene at strain rates above the inverse Rouse time, melts show steady extensional viscosity $\\eta_E \\sim \\mathrm{eps}_{dot}^{-1/2}$ while semidilute and concentrated solutions with matched entanglement number show extensional hardening, in conflict with tube models including chain stretch. Identify the mechanism (proposed: flow-induced reduction of monomeric friction by segment orientation) and predict $\\eta_E(\\mathrm{eps}_{dot})$ for melts and solutions from one theory.","problem_ref":null,"references":"","settled_by":"A constitutive model with independently measured parameters that reproduces eta_E(eps_dot) for melts and solutions, supported by rheo-optical or simulation measurements of the friction coefficient under flow.","status_note":"Steady thinning of PS melts in fast extension was reported in 2003 (Bach, Almdal, Rasmussen and Hassager, Macromolecules, https://doi.org/10.1021/ma034279q); the friction-reduction explanation is not universally accepted.","title":"Why entangled melts and solutions differ in fast extensional flow","topic_ref":"aeb1d914c5245c3ac0eb6390c11efb8e31b123b88f6954758542aa7f4dbb81e4"},"attested":{"attestation":{"batch":null,"client_id":null,"id_token_sha256":null,"kind":"platform"},"record_hash":"5561b3e75091c150147b66731e8e6b93e34a957b19e63321aebc2238198dfe26","schema":"pubphys.attested/1"},"envelope":{"attested_hash":"76dda0ff5a412fed705dd7f7c624065e1753b89ae5cae11acdf9679108eecb1d","platform_signature":{"key_id":"c6afc19b31429869751f06879c75cd64ea92654423d15b44be775bf1310a60da","sig":"NAFWYXANvt8yUu2lU73IQSq4KQhW0en9fPa-WISbi7saS32L1iKL4v7umkMMY1ec181KfDM6omyJ0spV2IXHDA"},"schema":"pubphys.envelope/1"},"record_hash":"5561b3e75091c150147b66731e8e6b93e34a957b19e63321aebc2238198dfe26","leaf_index":822}