Keywords: thermal polymerization, UV graft-polymerization, Styrene-butadiene-styrene

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Wilfrid Terence Page
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1 Materials Science Forum Vols (7) pp online at (7) Trans Tech Publications, Switzerland Comparison with Physics and Chemical Property of /AA Copolymer Using Thermal Polymerization and UV Graft-Polymerization Methods Ko-Shao Chen 1,a, Su-Chen Chen 1, Yi-Chun Yeh 1, Hong-Ru Lin 2,b, Wen-Fu Lee 3,c, Heng-Hsien Lee 3 1 Department of Material Engineering, Tatung University, TAIWAN 2 Department of Chemical Engineering, Southern Taiwan University of Technology, TAIWAN 3 Department of Chemical Engineering, Tatung University, TAIWAN a kschen@ttu.edu.tw, b hrlin@mail.stut.edu.tw, c wflee@ttu.edu.tw Keywords: thermal polymerization, UV graft-polymerization, Styrene-butadiene-styrene Abstract This study was compare of physics and chemical property of Styrene-butadiene-styrene ()/ Acrylic acid (AA) copolymer after thermal polymerization and UV graft-polymerization. The result of this study shows: when the thermal polymerization was used, the grafting percentage of -g-aa rose along with the increase of the AA monomer concentration. The maximum occurred when =.5g and AA=2.5 x.65mol, then it decreased along with the increase of the AA concentration. The transition ratio and grafting percentage decreased as the concentration of increased; while AA was fixed on.65mol, the maximum grafting percentage occurred by using 1g. The grafting percentage increase along with the increase of reacting time, and it reached the maximum after reacting 3 hours. The water contact angle was lowered from 82 o to 58 o. Using the UV graft-polymerization, when AA monomer concentration increased, the grafting percentage increased as well; the maximum occurred when AA concentration was 2.88M. Moreover, the grafting percentage was increasing along with the increase of reacting time, but it stopped increasing around minutes reacting time. The grafting percentage of thermal polymerization was higher than UV graft-polymerization. It shows that the swelling ratio of membranes grafted using the UV light was higher than those grafted by thermal polymerization. Introduction Styrene-Butadiene-Styrene (), a type of Thermal Plastic Rubber (TPR), can be fused in high temperature. Under normal operating temperature, it has the thermoforming characteristics of traditional thermoplastic and the characteristics of vulcanized thermosetting rubber. Because of its high air infiltration, elasticity and adherence, can be used as patches of adhesive and sole, and can be applied extensively on general industrial products [1-4]. However, due to the limitation of rubber s ingredients of the low surface free energy of common polyolefin TPR and the bad wettability, the application is limited. Therefore, the improvement of rubber s quality still has the importance and the space in further development. Traditionally, the composite method was commonly used in the quality improvement of rubber to strength its mechanical characteristics. For examples, mixing PS/BR/ together can produce the All rights reserved. No part of contents of this paper may be reproduced or transmitted in any form or by any means without the written permission of the publisher: Trans Tech Publications Ltd, Switzerland, (ID: /1/7,17:47:)

2 1289 THERMEC 6 different levels of compatibilities of the composites [5,6]. The mixer method, which is adding different ratio of sulfur onto and using heat and pressure to form the cross-linking among sulfur and chain segment, can increase the strength of in high temperature and keep the fluidity of. However, this method has the difficulty in controlling the surface structure of the material so the chemical treatment has been used [7,8].The chemical treatment uses the epoxidation to make the nonpolar structure of PB block of to produce the oxypolar group, and increases its adhesion and oil resistance. Another grafting method has been used to change the quality of rubber, too. According to the existing literatures, using the UV radiation to produce the -g-vp grafting copolymer and to improve its surface wettability and function [9] can also strengthen the mechanical strength of materials. This study used new method - UV graft-polymerization to improve the surface wettability and function of rubber. Commonly thermal polymerization method also to used to graft Acrylic Acid (AA) monomer onto block copolymer to improve its wettability. This study discussed the changing of membrane structure and wettability that were produced by these two polymerizations, and the influences of monomer concentration, reaction time, response of liquid density, etc. on grafting percentage. Experiment 1. Materials Styrene-butadiene-styrene () monomer was purchased from Shell company. Acrylic acid (AA) was purchased from Fluka. Riboflavin (B 2, C 17 H N 4 O 6 ) adopted to reduce the oxygen concentration during the polymerization process was purchased from Sigma Chem. Company. UV Hg lamp (W) AA AA Outlet vacuum oven 24 hr (b) Schematic of (a) thermal polymerization and (b) UV graft-polymerization. AA Product Product 2. Thermal polymerization.5 ~ 2.5 g was dissolved in a ml toluene solvent at 75 in a flask equipped with stirrer, thermometer, condenser and nitrogen inlet..2 g BPO and.3 ~ 3 (.65 mol) AA were also added in the same time. The reaction was terminated after 1 ~ 6 h. Then, put the product in the vacuum oven to 24 hr. Poly(AA) were reduced by methanol and air-dried at room temperature. The homopolymer was extracted by Cyclohexane, and the grafted was obtained after drying. 3. UV graft-polymerization was individually placed on the surface of lower electrode. The plasma system (Model PD-2S) manufactured by SAMCO, Japan, was first pumped to a base pressure of mtorr before plasma treatment. When the vacuum index was stable at mtorr, the argon gas was continuously introduced into the reactor and adjusted to working pressure for a stable period of time. Then the plasma was activated by RF generator (13.56 Hz). Then, 1 ~ 9 (.65mol) AA aqueous solution was prepared,.1 g/l riboflavin (B 2 ) was subsequently mixed with the AA solution in the ratio of AA : riboflavin = 4 : 1.

3 Materials Science Forum Vols The was immersed into the AA solution in the Pyrex glass container. This container was sealed and then irradiated with W UV light (wavelength: 365 nm, Henchman Co. Inc., Taiwan) ~ 5 min. After the graft polymerization reaction, the homopolymer of PAA was removed by washing in distilled water at 5 o C for 24 h under continuous stirring. 4. Characterization Swelling behavior of the /AA copolymer in distilled water was observed by measured the soaking weight variation. The swelling ratio was calculated according to the following equation: Swelling ratio = (W s W ) / W where W and W s indicated weights of dried and swollen samples, respectively. The hydrophilicity on the surface of substance was observed by water contact angle (θ H2O ) for each treatment (Gonio-meter type G-1 made by Erma Optical Works Co. LTD.). The surface morphology of modified fabric was observed from SEM (Hitachi S-8 and JSM-6). Attenuated Total Reflection (ATR, E, JASCO) spectroscopy was used to confirm chemical characterization of surface modified membranes. Result and discussion 1. Thermal polymerization grafted -AA membrane Fig. 1 is the graph of comparison of the grafting percentage to the ratio of butadiene and AA molar within. It used the fixed on.5g to compare the effectiveness and influence in different numbers of AA molar. When the molar ratio was between.5 and 1, the grafting percentage increased very fast from % to 58% along with the increase of monomer concentration of AA. Then, the grafting percentage increased slowly when the molar ratio was 1:2.5. It reached the maximum %, and then decreased slightly. This result shows that too many AA was not good for the reaction of grafting. Instead, it synthesized Poly (AA) because of the effectiveness of chain transfer. Fig. 2 used the fixed AA on.65mol to compare the influences of different contents to grafting percentage. Fig. 2 shows when was 1g, the grafting effectiveness reached its maximum; then with the increase of, the grafting percentage decreased. Because as dissolved in toluene, it formed a sticky liquid and increased the viscosity of reaction system. Therefore, the reaction is lowered. Fig. 3 used the fixed density of and AA to compare the influences of different reaction time to grafting ratio and percentage. Fig. 3 showed that the grafting ratio of AA reached the maximum after the 6-hour reaction time, but the grafting percentage became stable and not increasing after 3 hours. It could be possible that the reaction system was not stable. Thus, the polymerization completed after 3 hours, and the further reaction would cause chain transfer of AA in the molecule chain Graft ratio % X 6.5X -3 mol AA/.5g Fig.1 Effect of AA molar within on thegrafting percentage by using thermal polymerization.

4 1291 THERMEC 6 Graft ratio (%) Graft ratio % butadiene /AA molar ratio Fig.2 Effect of butadiene and AA molar ratio on grafting percentage by using thermal polymerization Reaction time(hr) Fig.3 Effect of reaction time on the grafting percentage by using thermal polymerization. 2. UV graft-polymerization Fig. 4 is the graph of the relation of AA molar and grafting percentage in UV graft-polymerization. Fig. 4 shows when the AA monomer concentration increased, the grafting percentage increased as well. The maximum occurred when the concentration of AA was 2.88M. But when the concentration was 2.88M, after washing the using distilled water, the poly (AA) still remained on the surface of membrane. The overall grafting percentage is not as high as using thermal polymerization. The possible reason could be that the UV graft-polymerization carries out not in the solvency, but only on the surface. Fig. 5 shows that the grafting percentage was increasing along with the increase of reaction time, it reached the maximum grafting percentage 14% at minutes, and then it decreased slightly along with the increase of time. Graft ratio(%) x 6.5x -3 mole AA/.5g Fig.4 Effect of AA molar within on thegrafting percentage by using UV graft- polymerization Graft ratio (%) Reaction time (min) Fig.5 Effect of reaction time on the grafting percentage by using UV graft- polymerization. 3. The relation of grafting percentage to the ratio of swelling balance Table 1 compared the relation of the grafting percentage of thermal polymerization and UV graft-polymerization to the water content and swelling ratio. The result showed that the swelling ratio of these products increased along with the increasing grafting percentage because of the existing wettability of AA. Therefore, the higher grafting percentage and the stronger wettability made the ratio of swelling balance larger. Generally, the thermal polymerization is greater because its grafting percentage is higher. The ratio of swelling balance will become larger if the grafting object is in alkaline liquid (ph=11.46), because the COOH will be dissociated as COO - in alkaline liquid. Since the homogeneous molecules repelled each other and opened the apertures, they enlarged the ratio of swelling balance.

5 Materials Science Forum Vols Table 1 The relation of the grafting percentage of thermal polymerization and UV graftpolymerization to the swelling ratio. Thermal polymerization UV graft-polymeri Grafting percentage (%) Swelling ratio (%) zation Table2 The wettability of before and after grafting AA by using thermal polymerization and UV graft-polymerization methods -g-aa (Thermal polymerization) Ar*/g-AA (UV graftpolymerization) θ H2O The water affinity of surface The differences of wettability of before and after grafting can be identified by measuring and comparing the water contact angle of AA grafted and non-aa grafted membranes of the. Table 2 is the variation of water contact angle of, which was grafted with AA. Table 2 shows that the angle was lowered from the original 82 o to 58 o after using thermal polymerization to graft, and it was lowered to 32 o by using the UV graft-polymerization. It shows that the wettability did exist on the surface of membrane, and the membrane s contact angle, which was produced by using the UV graft-polymerization, was lower than the one using the thermal polymerization. Membranes that were produced by these two methods have different characters. The UV graft-polymerization occurred only on the surface, but the thermal polymerization was grafting inside the membrane. Therefore wettability percentage of membrane, which was grafted by using the UV light polymerization, was higher. 5. Chemical structure Fig. 6 is the ATR/FTIR graph of membranes (a) grafted with AA using the UV graft-polymerization (b) and thermal polymerization (c). Comparing (a) and (b), the graph shows that the absorption peaks occurred at 118 cm -1 for ether carbon bands (-C-O), at 17 cm -1 for C=, and at cm -1 for carboxylic acid (-COOH). Observing (c), the situation of grafting membranes with AA using thermal polymerization was similar. They proved the existence of graft layers. %T -Chem.graft -UV-graft -subs. cm -1 Wavenumber Fig.6 ATR/FTIR of (a) membranes, (b) grafted with AA using the UV graft-polymerization, and (c) thermal polymerization. 6. Observation of SEM morphology Fig. 7 is the SEM morphology of membranes (a) grafted with AA using the UV graft-polymerization (b) and thermal polymerization (c). For the membranes that were grafted by the thermal polymerization, there was no significant change on the surface; but the graft layer could

1293 THERMEC 6 be seen clearly for those grafted by UV graft-polymerization. It shows that there were not many connections between the appearance of membranes and grafting percentage. (a) (b) (c) Fig.

When the thermal polymerization was used, the grafting percentage of -g-aa rose along with the increase of the AA monomer concentration and reacting time. The maximum occurred when =1g, AA=2.5 x.

The swelling ratio rose along with the increase of grafting percentage, and the water contact angle was lowered from 82 o to 58 o. 2.

6 1293 THERMEC 6 be seen clearly for those grafted by UV graft-polymerization. It shows that there were not many connections between the appearance of membranes and grafting percentage. (a) (b) (c) Fig.7 SEM morphology of (a) membranes, (b) grafted with AA using the UV graft-polymerization, and (c) thermal polymerization. Conclusion 1. When the thermal polymerization was used, the grafting percentage of -g-aa rose along with the increase of the AA monomer concentration and reacting time. The maximum occurred when =1g, AA=2.5 x.65mol and reacting time=3 hours, then it decreased along with the increase of the AA concentration and reacting time. The swelling ratio rose along with the increase of grafting percentage, and the water contact angle was lowered from 82 o to 58 o. 2. Using the UV graft-polymerization, when AA monomer concentration increased, the grafting percentage increased as well; the maximum occurred when AA concentration was 2.88M. Moreover, the grafting percentage was increasing along with the increase of reacting time, but it stopped rising around minutes reacting time. 3. The grafting percentage of thermal polymerization was higher than UV graft-polymerization. This result corresponds to the water contact angles. It shows that the swelling ratio of membranes grafted using the UV light was higher than those grafted by thermal polymerization. Reference 1. G. Hoiden, E. T. Bishop, N. R. Legge: J Polym Sci C Vol. 26 (1969), p Y. Ikada: Biomaterials Vol. 15 (1994), p A. H.Trinh, A. Rameshwar, H. M. Goerg: Polymer Vol. 44 (3), p A. H. Trinh, H. H. Le, A. Rameshwar, W. Roland, H. M. Goerg, K. Konrad: Polymer Vol. 44 (3), p P.H.P. Macau bas, N.R. Demarquette: Polymer Vol. 42(1), p N. Tomita, S. Tamai, E. Okajima, Y. Hirao, K. Ikeuchi, Y. Ikada: J Appl Biomater Vol. 5 (1994), p A. Zhang, C. Li: European Polymer Journal Vol. 39 (3), p Z. B. Zhou, H. Y. He, Z. Y. Weng, C. X. Zhao: Journal of Fluorine Chemistry Vol. 4(), p J. M. Yang, K. Y. Hsu: J Membr Sci Vol. 153 (1999), p.175

Supporting Information

Supporting Information Anion Conductive Triblock Copolymer Membranes with Flexible Multication Side Chain Chen Xiao Lin a,b, Hong Yue Wu a, Ling Li a, Xiu Qin Wang a, Qiu Gen Zhang a, Ai Mei Zhu a, Qing