(196ad) Interaction Between Supercritial CO2+Cosolvent and Poly(vinyl acetate)

Interaction between
Supercritial CO₂+Cosolvent and Poly(vinyl acetate)

Dong-dong Hu, Lei Bao, Ling Zhao, Tao Liu*

 (Shanghai Key Laboratory of Multiphase Materials
Chemical Engineering, East China University of Science and Technology, Shanghai
200237, China)

hudd@ecust.edu.cn; liutao@ecust.edu.cn;

Phone: (+86) 21 64253470; Fax: (+86) 21
64253528

Supercritical carbon
dioxide (scCO₂) is of interest as a potential alternative to conventional
organic solvents. Unfortunately, the low solvating power of scCO₂
restricts its compatibility with
polymers. Poly(vinyl acetate) (PVAc) was reported as one of the most CO₂-philic
hydrocarbon homopolymers, which was a significant step forward. But even so, the solubility of PVAc is very low, making them unsuitable to
apply on a large scale.

The cosolvents (ethanol,
acetone, n-heptane, denoted by ET, AC and C7) were introduced
to form CO₂+cosolvent systems for improving the solvent-solvent and solvent-solute interactions and
enhancing the the compatibility with PVAc. Comparing the interaction of CO₂
with acetone, and n-heptane, it could be
seen that ethanol and CO₂ provided stronger interaction energy from
the ab initio calculation due to the shortest distance between the C atom of CO₂
and the O atom of ethanol (Fig. 1). The molecular dynamic modeling showed that the
interaction between ethanol and CO₂ was
strongest due to the bigger solubility parameter of ethanol (Fig. 2) and the
obvious hydrogen bond bewteen ethanol and CO₂(Fig. 3), which increased
significantly the solubility parameter of solvent and improved the dissolution of polymers in CO₂.
The dissolution behavior measurement (Fig. 4) confirmed that the addition of
cosolvent could enhance the compatibility between CO₂ and PVAc to a
certain extent, and the solubility of PVAc
in scCO₂+cosolvent increased with the mole
fraction of cosolvent, which has a good agreement with the simulated results of
the solvent-solvent, solvent-solute interactions and the solubility parameter analysis.

Fig.
1 Most stable mode in ET/CO₂, AC/CO₂ and
C7/CO₂systems.

(a) ET/CO₂/CO₂;
(b) AC/CO₂;(c) C7/CO₂

Fig. 2  Solubility parameter
of CO₂-ethanol binary systems with different compositions

(a) ET/CO₂/CO₂;
(b) AC/CO₂;(c) C7/CO₂

Fig. 3  Comparison
of rational correlation functions    Fig.4  Cloud point
pressures of PVAc in

   between CO₂-ethanol
and CO₂-acetone systems.         
CO₂+solvent at different temperatures

Acknowledgement:

The authors are
grateful to the National Key Research and Development
Program of China(2016YFB0302201) and the National Science Foundation of China (21376087)
and Plan for Shanghai excellent technical leaders (14xd425500) for support.

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