{"record":{"author":{"account_ref":null,"orcid":null},"builds_on":[],"content_schema":"pubphys.content.revision/1","content_sha256":"e70b6793b4e29169285ef9ebbe491b367d230f4a4bf3404449ff8b5d2d0dd206","created":"2026-10-03T07:17:57Z","files":[],"origin":{"assisted_by":[],"kind":"seed"},"parents":["5475cf5dc5b1a72283d26dc95dc6e00d7ea4e00096a7c6492e409a1816eeb011"],"salt":"5370cbba81074895461a0e6c51a0dd3fb33ebed2ed180b47c1251cc4d3322a85","schema":"pubphys.record/2","site":"pubphys.com","target":null,"type":"revision"},"content":{"answer_type":"mechanism","assisted_by":[],"external_id":"bio.polymer-dynamics.thin-film-tg","kind":"phenomenon","literature_status":"contested","n":"1","parents":[],"plain":"Very thin polymer films soften at temperatures tens of kelvin lower than the bulk material. Why, and why the effect depends on chain length in free-standing films, is debated.","posed_since":"","precise":"Free-standing polystyrene films thinner than about 8e-6 cm (800 Angstrom) show $T_g$ reductions of tens of kelvin relative to bulk, with a dependence on molecular weight not seen in supported films. Determine whether the reduction arises from a mobile surface layer propagating into the film, from chain confinement or from another mechanism, and predict $T_g(h, M)$ for film thickness h and molecular weight $M$.","problem_ref":null,"references":"","settled_by":"A theory that predicts $T_{g}(h, M)$ for free-standing and supported films and agrees with measurements of local mobility profiles across the film.","status_note":"","title":"Why the glass transition temperature drops in thin polymer films","topic_ref":"aeb1d914c5245c3ac0eb6390c11efb8e31b123b88f6954758542aa7f4dbb81e4"},"attested":{"attestation":{"batch":null,"client_id":null,"id_token_sha256":null,"kind":"platform"},"record_hash":"74d4ea5b0c51fcaa9aae3890d7ae81ba62aae73a2fdb2d28e8033b4ef8808e08","schema":"pubphys.attested/1"},"envelope":{"attested_hash":"50d8c1d376357341391c48c36a42da071fbec371cc964893dc103c07a7199ccc","platform_signature":{"key_id":"c6afc19b31429869751f06879c75cd64ea92654423d15b44be775bf1310a60da","sig":"117aW5uoj4wLTyXy6OvWfLrpOaceMmq0sDtSb1ObrjWcWRGFh3YPhS3tP0y7WEl5iKxCtyNhcH2t-rhn6urSCg"},"schema":"pubphys.envelope/1"},"record_hash":"74d4ea5b0c51fcaa9aae3890d7ae81ba62aae73a2fdb2d28e8033b4ef8808e08","leaf_index":826}