Surface graft polymerization of N-vinylcaprolactam onto polylactic acid film by UV irradiation
- 325 Downloads
Graft polymerization of N-vinylcaprolactam (VCL) onto the surface of a polylactic acid (PLA) film was performed using a versatile and nondestructive technique. The method used consists of two steps. In the first step, a surface initiator is formed on a substrate under UV irradiation in the presence of a benzophenone (BP) solution, which promotes photoinitiation under UV irradiation at room temperature and under nitrogen. In the second step, the monomer (VCL) is grafted onto the substrate (PLA) by a living polymerization initiated by the surface photoinitiator. The hydrophobic polylactic acid film (PLA) became hydrophilic after grafting; the contact angle of the modified surface decreased drastically from the original value of 77° to <58° within 50 s of irradiation. The surface photografting parameters [polymerization rate (C p), grafting percentage (C g), and grafting efficiency (E g)] were derived using a gravimetric method in which the grafting yield could be controlled by varying the irradiation time or the monomer concentration. The first-derivative UV spectrum recorded between 200 and 360 nm was used as a sensitive tool to follow the grafting process at different times; the signals from VCL at 265 and 310 nm increased in size as the irradiation time increased due to the increase in VCL polymer units during the grafting process. FTIR-ATR analysis exhibited a clearly defined absorption band at 1,620–1,640 cm−1, corresponding to C=O stretching vibrations in the amide groups of unstrained rings in poly(N-vinylcaprolactam) (PNVCL). These analytical techniques confirmed the successful surface graft polymerization of VCL onto the polylactic acid film.
KeywordsPhotografting Polylactic acid Surface modification UV spectroscopy Vinylcaprolactam Grafting efficiency
The authors express their gratitude to CONACYT for their financial support of this project (S53075Y).
- 1.Gunatillake PA, Adhikari R (2003) Eur Cell Mater 5:1–16Google Scholar
- 2.Chromecek RC, Friends GD, Wissman LY, Yourd RA (1984) US Patent No. 4436887Google Scholar
- 11.Auras R, Harte B, Selke S (2005) In: Proc 63rd Annu Tech Conf Exhibit of the Society of Plastics Engineers, Boston, MA, USA, 1–5 May 2005, pp 3240–3244Google Scholar
- 20.Garbassi F, Morra M, Occhiello E (1998) Polymer surfaces: from physics to technology. Wiley, New YorkGoogle Scholar
- 22.Weiser WE, Pardue HL (1983) Clin Chem 29(9):1673–1677Google Scholar
- 24.Kirsh YuE (1998) Poli-N-vinilpirrolidon i drugie poli-N-vinilamidy [Poly(N-vinylpyrrolidone and other poly(N-vinylamide)s]. Nauka, Moscow, p 133Google Scholar
- 25.Smith A (1982) Prikladnaya IK-spektroskopiya polimerov. Mir, Moscow, pp 308–331 (translation of: Applied infrared spectroscopy, Wiley, New York)Google Scholar