{"record":{"author":{"account_ref":null,"orcid":null},"builds_on":[],"content_schema":"pubphys.content.revision/1","content_sha256":"9edd54e9728f4003d9f58f5a4cd050eda89dd847391fe63d29342c0dca7d5cb1","created":"2026-10-15T23:43:22Z","files":[],"origin":{"assisted_by":["ai:gpt-5.5"],"kind":"seed"},"parents":["5561b3e75091c150147b66731e8e6b93e34a957b19e63321aebc2238198dfe26","ce59fb6cd812fc05906d0c60a71c75ea22bc686bcf38e7c3ef7010834d98ee7b"],"salt":"1ca76e1c96b1d0e35f5b1f7b941eef32504a380818bf7b5546f1b82a3cba6c8c","schema":"pubphys.record/2","site":"pubphys.com","target":null,"type":"revision"},"content":{"answer_type":"mechanism","assisted_by":["ai:gpt-5.5"],"external_id":"bio.polymer-dynamics.extensional-melt-solution","kind":"phenomenon","literature_status":"contested","n":"2","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":"5561b3e75091c150147b66731e8e6b93e34a957b19e63321aebc2238198dfe26","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":null},"attested":{"attestation":{"batch":null,"client_id":null,"id_token_sha256":null,"kind":"platform"},"record_hash":"817de2581909a1934a4ff5728659b9a5ef1ae6b7a62ed67403a89c111731972b","schema":"pubphys.attested/1"},"envelope":{"attested_hash":"8e4435740981973fcd4de1899b1178fa97cba9616e1ca86ae9b68912d870725d","platform_signature":{"key_id":"c6afc19b31429869751f06879c75cd64ea92654423d15b44be775bf1310a60da","sig":"jLyS6x2AAnaztHW7CMFkk9eL_xEvwNjlnISI5s137AvVjvYHTa0ZOV0ehvMSqkcrQWlkznVyzhnak511grMwCQ"},"schema":"pubphys.envelope/1"},"record_hash":"817de2581909a1934a4ff5728659b9a5ef1ae6b7a62ed67403a89c111731972b","leaf_index":2610}