Surface characteristics of UV-irradiated chitin-based shape memory polyurethanes
Khalid Mahmood Zia
a
, Mohammad Zuber
a,
*
, Shahid Mahboob
b
, Tayyaba Sultana
c
, Salma Sultana
b
a
Department of Industrial Chemistry, GC University, Faisalabad 38030, Pakistan
b
Department of Zoology, GC University, Faisalabad 38030, Pakistan
c
Department of Bioinformatics, GC University, Faisalabad 38030, Pakistan
article info
Article history:
Received 3 October 2009
Received in revised form 5 November 2009
Accepted 9 November 2009
Available online 13 November 2009
Keywords:
Chitin
Dimethylol propionic acid
Shape memory polyurethane
UV-irradiation
Surface free energy
abstract
Shape memory polyurethanes (SMPUs) were prepared from polycaprolactone diol 4000 (PCL 4000), 4,4
0
-
diphenylmethane diisocyanate (MDI), 1,4-butanediol (BDO), chitin, dimethylol propionic acid (DMPA),
and triethylamine (TEA). The synthesized samples were irradiated for 50, 100, and 200 h in an UV expo-
sure unit. The effects of chitin and DMPA contents in the polyurethane (PU) formulation on surface prop-
erties of the UV-irradiated PU samples were investigated by contact angle measurements, surface free
energy and water absorption (%), total work of water adhesion to polymer and equilibrium degree of
swelling. Results of the aforementioned surface techniques revealed that the UV-irradiated PU samples
were affected by varying the UV exposure period. The interactions of the PU films with solvents on the
surface were clearly related to the contents of DMPA and chitin in the final polyurethane formulation
and UV-irradiation time.
Ó 2009 Elsevier Ltd. All rights reserved.
1. Introduction
Chitin is considered the second most plentiful organic resource
on the earth; occurring in plants, marine invertebrate, insects, cell
walls of some fungi, and microorganisms (Gorovoj & Burdukova,
1996; Knorr, 1984; Muzzarelli, 1977). Shape memory polymers
(SMPs) are polymer networks equipped with suitable molecular
switches, which are sensitive to an external stimulus. Among var-
ious SMPs, shape memory polyurethanes (SMPUs) are receiving
much attention for their easy control of glass transition tempera-
ture (T
g
) around the room temperature and excellent shape mem-
ory properties at the room temperature. A series of SMPUs from
polycaprolactone diol, 1,4-butanediol (BDO), dimethylol propionic
acid (DMPA), and 4,4
0
-diphenylmethane diisocyanate (MDI) or tol-
uene diisocyanante (TDI) were synthesized (Han, Boung, & Byung,
2001; Hu, Yang, Yeung, Ji, & Liu, 2005; Jeong, Lee, Lee, & Kim, 2000;
Kim, Lee, & Xu, 1996; Kim et al., 1998; Lee, Chun, Chung, Sul, & Cho,
2001; Li, Chen, Zhu, Zhang, & Xu, 1998; Li et al., 1996). Extensive
work on detailed molecular characterization (Zia, Barikani, Zuber,
Bhatti, & Sheikh, 2008a), XRD studies (Zia, Bhatti, Barikani, Zuber,
& Sheikh, 2008b), and thermal properties (Zia, Barikani, Bhatti, Zu-
ber, & Bhatti, 2008c) of chitin-based polyurethane elastomers
(PUEs) have also been previously discussed and reported. In vitro
biocompatibility and non-toxicity of chitin/1,4-butanediol blends
based polyurethane elastomers has also been reported elsewhere
(Zia, Zuber, Bhatti, Barikani, & Sheikh, 2009a, 2009b). Some reports
are also available on molecular characterization and shape mem-
ory properties of chitin-based shape memory polyurethane elasto-
mers (Barikani, Zia, Bhatti, Zuber, & Bhatti, 2008; Zia, Zuber,
Barikani, Bhatti, & Khan, 2009c).
For the application of PU, their stability against terrestrial
weathering is important. One of the greatest factors in the terres-
trial weathering of PUEs is ultraviolet (UV) radiation in the wave-
length range 330–410 nm. Attempts have been made to study
the effect of UV-irradiation on surface properties of some common
polymers (Kaczmarek & Chaberska, 2006; Kaczmarek & Podgorski,
2007; Zia, Bhatti, & Bhatti, 2007). Photooxidative behavior and ef-
fect of chain extender length in polyurethane on photooxidative
stability have also been reported (Zia, Barikani, Zuber, Bhatti, & Is-
lam-ud-Din, 2008d). Surface morphology of starch (Matsushita
et al., 2008), cellulose (Yokota, Kitaoka, & Wariishi, 2008), and chi-
tin–humic acid (Santosa, Siswanta, Sudiono, & Utarianingrum,
2008) have also been investigated and well documented. XRD
studies and surface characteristics of UV-irradiated and non-irradi-
ated chitin-based polyurethane elastomers have also been pre-
sented elsewhere (Zia, Barikani, Khalid, Honarkar, & Ehsan-ulHaq,
2009g; Zia, Barikani, Zuber, Bhatti, & Barmar, 2009e, 2009f; Zia,
Bhatti, Barikani, Zuber, & Bhatti, 2009d). No reference is still avail-
able on the study of the effect of different exposure time of UV
radiation on surface characteristics of chitin/DMPA/BDO-based
shape memory polyurethane elastomers. In this work, ultraviolet
(UV) radiations were used to irradiate a series of polyurethane
elastomers based on PCL, 4,4
0
-diphenylmethane diisocyanate
(MDI), chitin, DMPA, BDO, and TEA. DMPA was used for preparing
the SMPU, since DMPA can give higher recovery strain and lower
0144-8617/$ - see front matter Ó 2009 Elsevier Ltd. All rights reserved.
doi:10.1016/j.carbpol.2009.11.015
* Corresponding author. Tel.: +92 321 6682375; fax: +92 41 9200671.
E-mail address: mohammadzuber@gmail.com (M. Zuber).
Carbohydrate Polymers 80 (2010) 229–234
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Carbohydrate Polymers
journal homepage: www.elsevier.com/locate/carbpol