{"record":{"author":{"account_ref":null,"orcid":null},"builds_on":[],"content_schema":"pubphys.content.revision/1","content_sha256":"b3bf17641ed193f5a3de70784a4a9a7701d223367f5022055d512309ae8eb2c6","created":"2026-10-15T23:43:22Z","files":[],"origin":{"assisted_by":[],"kind":"seed"},"parents":["74d4ea5b0c51fcaa9aae3890d7ae81ba62aae73a2fdb2d28e8033b4ef8808e08","ce59fb6cd812fc05906d0c60a71c75ea22bc686bcf38e7c3ef7010834d98ee7b"],"salt":"6641770169268bcd7ca65f5dbde5a5d7d68a2f9b27094dd5e60b52462c56969a","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":"2","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 $8 \\times 10^{-6}$ 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":"74d4ea5b0c51fcaa9aae3890d7ae81ba62aae73a2fdb2d28e8033b4ef8808e08","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":null},"attested":{"attestation":{"batch":null,"client_id":null,"id_token_sha256":null,"kind":"platform"},"record_hash":"7d9770cdb54583d28779afee258f28369a24d2a1f32ee0e8ab5f0bb90fad54f3","schema":"pubphys.attested/1"},"envelope":{"attested_hash":"b5e54e4295f1e454c22c8c99f17d43e88c861c632c538da57fc63159abd757b8","platform_signature":{"key_id":"c6afc19b31429869751f06879c75cd64ea92654423d15b44be775bf1310a60da","sig":"dsL43dWyor2uw4tIJnrsfmEl0I7CteysZezuKwjdROI94tgLlJhjes-eAZM2vywCwHujDVfZuFnN37yteXJTDg"},"schema":"pubphys.envelope/1"},"record_hash":"7d9770cdb54583d28779afee258f28369a24d2a1f32ee0e8ab5f0bb90fad54f3","leaf_index":2616}