Detailed Compositional and Structure–Property Analysis of Ethylene Oxide-Propylene Oxide Triblock Copolymers

Abstract

The polyethylene oxide-polypropylene oxide (PEO-PPO) based triblock copolymers are notable amphiphilic copolymers with a diverse range of applications. The presence of homo-, and/or diblock impurities in copolymers with PEO-PPO-PEO triblock has been demonstrated. This finding suggests that the samples are blends rather than pure triblock copolymers. Furthermore, copolymers with triblock copolymer content of 0 or less than 20% by molar percentage have been identified. The hydrophilic-lipophilic balance (HLB) is also calculated based on the exact composition of the blends. The effect of HLB values and compositional data on the initial foam height (in casein solution), the surface tension, and the contact angle are investigated. The correlation coefficients for the PPO-PEO-PPO copolymers versus HLB values are found to be high, while those obtained for the PEO-PPO-PEO copolymers versus values of HLB are significantly lower. The lower correlation coefficients for the PEO-PPO-PEO samples can be attributed to the presence of homo- and diblock (co)polymer contaminants. In addition, a linear regression model has been constructed to find a mathematical relationship between the percentage of ethylene oxide, the average number of propylene oxide units, and the properties of the copolymer.