Castor oil and PEG-based shape memory polyurethane films: effect of chain extender amount on some polymer properties and performance

Abstract

A series of polyurethane (PU) films were synthesized via one-shot bulk polymerization with polyethylene glycol, castor oil, hexamethylene diisocyanate, and 1,4-butanediol (BD) at three different chain extender ratios. Since it was found in our previous study that hard segment content is more effective on shape memory property than soft segment length (Bonfil, M., Sirkecioglu, A., Bingol-Ozakpinar, O., Uras, F., Güner, F. S. J. Appl. Polym. Sci. 2014, 131, 1-12), in this study the effects of BD amount on some physical properties, thermal properties, and shape memory performance of the films were investigated. Shape fixity and shape recovery were achieved under two different cooling/heating regimes.The amount of BD is an important parameter affecting the physical properties, chemical structure, and thus shape memory performance. Decreasing the BD amount increased the crystallinity and the films, being of relatively high crystallinity, showed the highest shape recovery ratio. Increasing BD amount in PU films increases the hydrogen-bonded structure and the films having a relatively high degree of hydrogen-bonded structure showed the highest shape fixity ratio. The samples showed higher shape memory performance at high cooling and heating rates. IntroductionSince the first shape memory polyurethanes were discovered in 1988 by Mitsubishi Heavy Industry, the research area has developed rapidly. In recent years, smart textile and biomedical applications have become the most promising fields for shape memory polyurethanes.Polyurethane (PU) is a special polymer composed of soft and hard segments in its structure. Hard segments consist of diisocyanate and chain extender. Soft segments are formed by long chain polyether or polyester glycols. Urethane groups have an ability to self-associate via hydrogen bonds between interurethane and urethane-ester or urethane-ether groups. 1 Due to the aggregation of hard segments via hydrogen bonds to form hard segment domains, which disperse in the soft segment matrix, a segmented structure and thus, microphase separation occur. 2,3 Interactions between the molecules of hard segments increase the phase separation between soft and hard segments and enhance the shape memory properties of polyurethanes. 4 Since soft segments show a thermal transition at transition temperature and they work like a reversible molecular switch point, the molecular weight and the amount of polyol in the polymer are important parameters. The type and the amount of chain extender, which is an indispensable component of the hard segments, are also important parameters, since hard segments are responsible for the original shape.

Forma-memoria poliuretano biobateragarriak

“…Entropia handiagoko egoerara bueltatuko da; hau da, energia gutxieneko eta egonkorreneko formara [3,4]. Polimeroaren egitura kimikoa eta morfologia kontrolatzean eta deformazio-pausoan baldintzak optimizatzean, hobetu daiteke forma-memoriaren etekina [5]. Material horien erabilerari dagokionez, medikuntzaren arloan abantaila anitzak azaltzen dituzte, bai material kirurgiko bai inplante modura.…”

“…Segmentu gogorra diisozianatoz eta kate hedatzailez osatuta dago; segmentu biguna, berriz, kate luzeko polieter edo poliester glikolez (poliol), 5a. irudian ikusten den bezala [5,8,9].…”

“…Horren ondorioz, segmentu gogorraren eta bigunaren faseak gehiago bereizten dira, eta ezaugarri horrek poliuretanoetan forma-memoria propietateak hobeak izatea eragiten du. Propietate horri esker, materiala trantsizio-tenperaturatik gora berotzen denean, bere hasierako forma berreskuratuko du [5,7,8].…”

Water Vapor Transport Properties of Polyurethane Films for Packaging of Respiring Foods

“…PU1500-70-40 coded film had the lowest density. At this point, the differences of density and structure of the monomers are needed to be noted (ρ CO = 0.96 g/cm 3 , ρ PEG1500 = 1.23 g/cm 3 , and ρ BDO = 1.015 g/cm 3 ) [6]. Density is a function of chemical composition, being dependent on the weight of individual molecules and the way they pack together.…”

“…In fact, if the mixed phase or non-H-bonded N-H stretching is available, a shoulder band on the highfrequency side around 3350 cm 1 would appear as shown in Fig. 2a [6,10]. In the C=O stretching region, a strongly hydrogen-bonded C=O peak at about 1682 cm -1 , indicating the presence of H-bonded urethane C=O groups for the ester structure, was observed for all film samples, and poorly H-bonded carbonyl was observed at about 1715 cm -1 for PU1500-70-50 and PU1500-70-60 coded samples (Fig.…”