Self-Assembly of the Triblock Copolymer 17R4 Poly(propylene oxide)14 - Poly(ethylene oxide)24 - Poly(propylene oxide)14 in D2O
Bryna C. Kumi, Boualem Hammouda, Sandra C. Greer
The triblock copolymer Reverse Pluronic 17R4 consists of tow end blocks of poly(propylene oxide)(PPO) with a middle block of poly(ethylene oxide) (PEO): PPO14-PEOd24^-PPO14, where the subscripts indicate the number of monomers in each block. We have investigated the three regions of the phase diagram of 17R4 in D2O by small-angle neutron scattering, supplemented by rheometry and dynamic light scattering. In region I, the cloudy solution contains the copolymer in large clusters made of hydrophobic PPO-rich "knots" bridged by dissolved hydrophilic PEO chains. These clusters vanish at low temperatures for low copolymer concentration. In region I over long times (weeks) at 25 °C, a white liquid/gel forms at the air-D2O interface; this phenomenon has not been reported previously, but we did not study this effect in detail. In region II at temperatures above the micellization line, the large clusters dissipate and unimers coexist with "flower Micelles," where the PPO blocks are the centers of the micelles and PEO blocks loop into the solvent. In region III at still higher phase of higher copolymer concentration is in region II, and the lower phase is in region I. The concentrated upper phase may contain micelles so crowded as to form a network.
, Hammouda, B.
and Greer, S.
Self-Assembly of the Triblock Copolymer 17R4 Poly(propylene oxide)<sub>14</sub> - Poly(ethylene oxide)<sub>24</sub> - Poly(propylene oxide)<sub>14</sub> in D<sub>2</sub>O, Journal of Colloid and Interface Science, [online], https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=915997
(Accessed December 2, 2023)