Molecular Design, Preparation, and Characterization of Fluoro-Containing Polyimide Ultrafine Fibrous Membranes with High Whiteness, High Thermal Stability, and Good Hydrophobicity.

Polymeric ultrafine fibrous membranes (UFMs) with high thermal stability and high whiteness are highly desired in modern optoelectronic applications. A series of fluoro-containing polyimide (FPI) UFMs with high whiteness, good thermal stability, and good hydrophobicity were prepared via a one-step electrospinning procedure from the organo-soluble FPI resins derived from a fluoro-containing dianhydride, 4,4'-(hexafluoroisopropylidene) diphthalic anhydride (6FDA), and various diamines containing either pendant trifluoromethyl (-CF3) groups or alicyclic units in the side chains. The obtained FPI UFMs, including FPI-1 from 6FDA and 3,5-diaminobenzotrifluoride (TFMDA), FPI-2 from 6FDA and 2'-trifluoromethyl-3,4'-oxydianiline (3FODA), FPI-3 from 6FDA and 1,4-bis[(4-amino-2-trifluoromethyl)phenoxy]benzene (6FAPB), FPI-4 from 4,4'-bis[(4-amino-2-trifluoromethyl)phenoxy]biphenyl (6FBAB), and FPI-5 from 6FDA and 4'-tert-butyl-cyclohexyl-3,5-diaminobenzoate (DABC) showed whiteness indices (WI) higher than 87.00 and optical reflectance values higher than 80% at the wavelength of 457 nm (R457), respectively. The FPI-5 UFM, especially, showed the highest WI of 92.88. Meanwhile, the prepared PI UFMs exhibited good hydrophobic features with water contact angles (WCA) higher than 105°. At last, the PI UFMs exhibited good thermal stability with glass transition temperatures (Tg) higher than 255 °C, and the 5% weight-loss temperatures (T5%) higher than 510 °C in nitrogen.

[Prospective cohort study on prevention of Frey syndrome in parotid surgery].

OBJECTIVE: To investigate the prevention of Frey syndrome after parotidectomy. METHODS: A prospective cohort study of 100 patients with parotid cancer who received parotid surgery was underwent in our hospital from 2001 to 2004. These patients were assigned to two groups, study group (50 cases) and control group (50 cases). The patients in the study group received parotidectomy and intraoperative placement of collagen pieces within the parotid bed, between the skin flap and the facial nerve. The patients in the control group received a conventional parotidectomy and no collagen pieces was implanted. All of the patients were followed-up and were evaluated for Frey syndrome with identical questionnaires. RESULTS: Compared with control group, the incidence rate of Frey syndrome was significantly decreased in the study group (20% vs 60%, chi(2) = 15.04, P < 0.001). Postoperative incidence of facial contour apparent deformity was 80% (40/50) in control group and 44% (22/50) in study group (chi(2) = 12.26, P < 0.001). CONCLUSIONS: Use of collagen pieces as an interposition fill barrier improves parotidectomy outcome by reducing the incidence of Frey syndrome, and it improves cosmetic results concurrently.