Laboratory of Polymer Chemistry, Eindhoven Polymer Laboratories, Eindhoven University of Technology, P. O. Box 513, 5600 MB Eindhoven, The Netherlands
Alkoxyamine-mediated Controlled Radical
Polymerization in Emulsion
Wilfred Smulders, Christianne Göttgens, Gilles Olive, Steven van Es
The increasing need for products with better performance and durability requires the use of speciality polymers with controlled composition and architecture. However, no industrial cost-effective process is presently available to synthesize such polymers. Moreover, current processes are performed in solvent media and need recycling of solvents and thorough removal of organic
residuals. Finally, these processes are incompatible with water, while the demand for waterborne systems is growing fast due to environmental concerns.
Controlled Radical Polymerization (CRP), especially when applied directly in emulsion, will be able to reconcile these conflicting
demands. In CRP all polymer chains allow stepwise addition of monomer throughout the whole process by limiting the extent of chain termination. CRP thereby allows for the sequential radical polymerization of monomers (multi-blocks) and construction of well-defined architectures.
The main innovations to be achieved within the project are:
increase in polymerization rate at temperatures below 100 °C
development of efficient process conditions and modelling controlled radical polymerization in emulsion
synthesis of copolymers with controlled composition and architecture targeted to market requirements within the field of PSA C O N R1 R2 C· + ·O N R1 R2 C(Mn) O N R1 R2 n M
Scheme of alkoxyamine-mediated controlled radical polymerization
Introduction
Results and discussion
Bulk polymerizations
These plots show that CRP of styrene at 90 °C is possible. These results indicate that an increase in reaction rate is obtained by introducing catalytic groups and open ring
structures, while control is maintained. Polydispersities are between 1.2 and 1.4 in all cases. However reaction rates will never be comparable to the rates of uncontrolled
polymerizations because the principle of this technique is
based on decreasing the radical concentration and thus the polymerization rate.
Conclusions
0 10 20 30 40 50 60 70 80 90 100 0 2000 4000 6000 8000 10000 12000 14000 16000 M n conversion [%] 0 20 40 60 80 100 120 140 160 0.0 0.4 0.8 1.2 1.6 2.0 2.4 2.8 3.2 3.6 ln ( [M ] 0 /[ M ]) time [h] O N P O O O R N O O N 0 20 40 60 80 100 0 5000 10000 15000 20000 M n conversion [%] 1.0 1.2 1.4 1.6 1.8 2.0 P D R N O Emulsion polymerizationsThese plots show that in principle it is possible to perform alkoxyamine-mediated CRP in emulsion. Both a linear
increase in molecular weight and polydispersities below 1.5 are observed. However in this case the rate is very slow,
even compared to the same reaction in bulk. This is
probably a consequence of the cage-effect, which does not allow the radical chain to propagate but gives rise to
immediate trapping by the nitroxide.
results of CRP of styrene at 90 °C in bulk
results of CRP of styrene at 90 °C in emulsion
0 50 100 150 200 250 300 350 0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 ln ( [M ] 0 /[ M ]) time [h]
There is a considerable effect of both structure and functional groups on kinetics. From this field improvements can be expected.
Alkoxyamine-mediated CRP in emulsion is possible, although a considerable increase in reaction rate is necessary. In order to optimize CRP in emulsion and increase the polymerization rate a full theoretical modelling and improved nitroxides are required.
