| Summary: | 碩士 === 逢甲大學 === 化學工程研究所 === 82 === Pannox 乳化劑 (Polyoxethylene nonylphenyl ether)系列在水中形成之
聚集體之旋轉半徑 (RG，以本性黏度換算) 隨分子內聚氧乙烯(PEO)鏈長
之增加而增加。其在水中之溶劑性及臨界微胞濃度(CMC)亦有相同趨勢。
十二烷基硫酸鈉 (SDS) 之加入可幫助溶解 Pannox，使聚集體表面之分子
鏈有較大之伸張，因而使RG變大。但同時使 CMC 提高此顯示使聚集程度
降低，此效應對 PEO 鏈較短者 (EO No.=12) 尤其顯著，使聚集體之 RG
變小。 Pannox 乳化劑之 PEO 鏈長愈長，在聚苯乙烯 (PS) 乳液粒子之
吸附面積愈大，且乳化劑吸附層厚度愈大。此使乳化聚合得到之粒徑，從
低轉化率到高轉化率均較小；且乳化聚合速率會較快。因此 PEO 鏈愈長
，對乳液之安定能力愈佳。當使用 SDS 當作共乳化劑時，於固定之
Pannox 用量下，乳化聚合速率隨 SDS 量之增加而先上昇後下降。 SDS
會幫助溶解 Pannox，使其在水中之溶解性增加，且使聚集程度降低。因
此 EO 值等於12之 Pannox 乳化劑在 PS 乳液粒子之吸附面積及吸附層厚
度均變大。EO 值大於12者在 PS 乳液粒子表面之吸附層厚度變小。除了
上列兩項因素之外，可能係由於 SDS 吸附於 Pannox 之 PEO 鏈上，使其
在乳液粒子之定錨點增加之緣故。因此, Pannox 乳化劑之 EO 質愈大,
其 CMC 質便愈高。此乃由於其溶解度增加, 使達到臨界微胞所需之乳化
劑濃度增加。同理, 混合乳化劑 ( SDS / Pannox )中, SDS 會幫助溶解
Pannox , 可增加其溶解度, 而提高 CMC 值。
The radius of gyration (RG) of the aggregates in water, formed
by Pannox surfactant(polyoxyethylene nonylphenyl ether) series
and determined from the intrinic viscosity, increases with
increasing the polyoxyethylene (PEO) chain length of Pannox.
Both the solvent power of water and the critical micelle
concentration (CMC) increases with increasing the PEO chain
length too. Sodium dodecyl sulfate (SDS) can solubilize and
extend Pannox surfactant molecular chains in water, thus the RG
of surfactants in water increase. Meanwhile the CMC is
increased, and thus the degree of aggregation is decreased.
This makes the Pannox with the shorter PEO chain (e.g., EO
No.=12) has a smaller RG. The pannoxes with the longer PEO
chains have the larger molecular area (Am) and thickness of
adsorbed layer (d) on polystyrene (PS) latex particles. In
addition, the recipe has the smaller latex particle size either
at low conversion or high conversion, and the higher rate in
the emulsion polymerization (EP) of styrene. This reveals the
greater stabilizing efficiency for the Pannox with the longer
PEO chain. Using sodium dodecyl sulfate as cosurfactant, with
the fixed concentration of Pannox, the rate of EP increases
first and then decreases with increasing SDS contration. The
SDS can solubilize the Pannox, and, therefore, increasing the
solvent power of water and decreasing the degree of aggregation
of Pannox. Therefore, the Pannox with EO No. of 12 has larger
values in Am and d than in the absence of SDS. Meanwhile, the
Pannoxes with EO No. of greater than 12 have smaller values in
d. The additional factor is attributed to the increasing
anchoring sites of Pannox on latex particles due to the
increasingly attaching of SDS on the PEO chains of the Pannox.
|
|---|
