Polymerization Kinetics of Acrylic Monomers in Aqueous and Non-Aqueous Systems

200 Pages·2017·5.64 MB·English

ETH Library
Polymerization Kinetics of Acrylic
Monomers in Aqueous and Non-
Aqueous Systems
Doctoral Thesis
Author(s):
Fischer, Eric J.
Publication date:
2017
Permanent link:
https://doi.org/10.3929/ethz-b-000227353
Rights / license:
In Copyright - Non-Commercial Use Permitted
This page was generated automatically upon download from the ETH Zurich Research Collection.
For more information, please consult the Terms of use.
DISS. ETH NO. 24697
Polymerization Kinetics of Acrylic Monomers
in Aqueous and Non-Aqueous Systems
A thesis submitted to attain the degree of
DOCTOR OF SCIENCES of ETH ZURICH
(Dr. sc. ETH Zurich)
presented by
Eric Jean Fischer
MSc ETH Chemical and Bioengineering
born on 09.06.1988
citizen of Luxembourg
accepted on the recommendation of
Prof. Dr. Massimo Morbidelli, examiner
Prof. Dr. Giuseppe Storti, co-examiner
Prof. Dr. Andrew deMello, co-examiner
2017

Acknowledgments
My first thanks are directed towards Prof. Massimo Morbidelli who initiated my
interest in the world of polymer engineering during the master studies, and who
gave me the opportunity to work in his group. I would like to thank Prof. Andrew
deMello for having accepted to guide me as co-examiner.
I am extremely grateful to Prof. Giuseppe Storti for supervising my thesis
throughout the ups and downs, for always being supportive and trusting in me.
Your guidance is a shining example for my future career and will always be re-
membered.
Special thanks also go towards Danilo with whom I had the chance to closely
work with, and who always was there to answer any question. Furthermore, I
would like to thank Manoj, who I was fortunate to supervise during his research
projects and who did an amazing work both experimentally and theoretically.
Especially your amazing presentation skills will never be forgotten.
I would also like to express my thanks to Marta Vidiella del Blanco, Anna
Pratsinis and Simon Matoori, who I was lucky to collaborate with in very different
but nonetheless fascinating research areas — you helped me to widen my horizon
far beyond the world of polymers.
Iexpressmydeepthankstothosepeopleintheresearchgroupwhowereclosest
to me and at my side in good and bad times and endured all of my moods: Thank
youJan-Georg, Marcel, Peter, Alberto, Antoine, Pooja, Vincent, Baptiste, Lucr`ece
II
and David. I would also like to further extend my thanks to the entire MM group,
including all current and former members: you all contributed into making my
stay in the group a very pleasant adventure.
IalsoacknowledgethecommitmentofmydearfellowIThomiesRushd,Ernesto
and Fabian, with whom I had the chance to share the burden of IT work — and
of the IT coordinators Erol Dedeoglu and Mathias Egloff.
I would also like to mention my friends from my ‘off-ETH’ life, especially all
those from aki and Cantata Nova. You made my years in Zurich special and I
share unforgettable memories with so many of you.
I would like to express my sincere gratitude to Celia, who was always there for
me and supported me in many ways, and who didn’t complain when I stayed in
the lab until (very) late. Without you, I would not have been able to accomplish
my thesis.
Last but not least, I would like to deeply honor the never-ending support of my
parents, siblings and extended family, who always encouraged me over all these
years to pursue my path.
Abstract
The careful control of the polymerization kinetics is a major step towards the de-
velopment of polymer products with controlled, tailored characteristics in various
industrial applications. In this work, monomers largely used in industry, acrylics,
have been considered. Two different processes have been explored, solution and
dispersion polymerization, each one exhibiting its own complexity for different
reasons.
In the case of polymerization in aqueous solution, as the understanding of
the kinetic behavior of ionizable monomers is yet limited, the propagation rate
of acrylic acid type monomers was studied in two cases: homopolymerization of
methacrylic acid and copolymerization of acrylic acid with acrylamide. It was
shown that the polymerization rate of ionized monomers is smaller compared
to their non-charged counterpart, and that the reaction rate increases with the
amount of charges in the reaction medium. A mathematical model was applied to
predict the corresponding propagation rate constant, taking into account a depen-
dence of electrolyte concentration in addition to the typical intrinsic propagation
rate. The model proved effective after suitable determination of the corresponding
parameter values. In the copolymerization study, the model was able to suc-
cessfully concur with literature data obtained by PLP, the to-date most reliable
method to determine polymer reaction rates.
Many polymers however are produced not in solution, but through hetero-
III
IV
geneous processes, such as emulsion or dispersion polymerization. This type of
processes appears especially useful when polymer particles are desired as final
product, such as applications for coating formulations, chromatography packing
materials, or liquid crystal display spacers. Again, the ability to control the reac-
tion rate is a key factor towards the steering of a final product quality and, in this
respect, to control the monomer concentration in all phases. Thus, a new method
was developed to determine partition coefficients combining accessible experimen-
tal approaches and suitable thermodynamic modeling, with the special advantage
of directly accessing the activity of all species at equilibrium. Saturation condi-
tions of single components in the polymer phase were analyzed below saturation
by increasing the amount of added solvent and nonsolvent to pure polymer, thus
in the absence of a liquid phase. Through this approach, binary interaction pa-
rameters were obtained for the system MMA/hexane/PMMA. With these param-
eters and the experimental activities in the ternary system, the partitioning of the
three components was determined in conditions where saturation conditions were
reached (presence of a considerably large liquid phase). Furthermore, this method
proved suitable to determine the effect of MMA/hexane solution addition onto the
polymer glass transition temperature (T ) due to plasticization of the polymer.
g
By identifying a change in the activity profile upon addition of solution, it was
possible to deduce the amount of solution necessary to reduce the glass transition
temperature of PMMA from its pure T to the operating temperature.
g
The dispersion polymerization of methyl methacrylate in hexane was studied
extensively to determine the effects of stabilizer concentration, stabilizer molecular
weight and monomer concentration on the kinetics and particle size distributions.
As anticipated, the experiments support a model considering two different reaction
loci: atthebeginning, thereactioninthecontinuousphaseisdominant, whilelater
on the reaction rate is dominated by the polymerization in the dispersed phase.
V
Additionally, above a certain threshold level of initial monomer concentration,
the rate of polymerization becomes independent of the particle size distribution.
This behavior is presumed to be due to diffusion limitations at low monomer
concentrations in cases with insufficient interfacial surface area. It was also shown
that the number of particles increases drastically at the beginning of the reaction,
before staying constant until the end of the reaction, while the individual particles
grow regularly in size upon conversion of monomer. Thus, the particle size can be
easily controlled a priori and adjusted through selection of the right initial recipe.
Finally, a mathematical model was developed to describe the reaction kinetics of
dispersionpolymerization, whichprovestheaforementionedseparabilityofparticle
size distribution and kinetic rate at high monomer concentrations in the MMA
dispersion polymerization system.

Zusammenfassung
Die sorgf¨altige Kontrolle der Polymerisationskinetik ist ein wichtiger Schritt zur
Entwicklung von Polymerprodukten mit kontrollierten, massgeschneiderten Eigen-
schaften in einer Reihe industrieller Anwendungen. In dieser Arbeit wurden Acryl-
basierte Monomere, die weitgehend in der chemischen Industrie verwendet werden,
untersucht. Es wurden zwei verschiedene Prozesse erforscht, n¨amlich die L¨osungs-
und Dispersionspolymerisation, die jeweils aus unterschiedlichen Gru¨nden ihre ei-
gene Komplexit¨at aufweisen.
Da das Verst¨andnis des kinetischen Verhaltens von ionisierbaren Monomeren
noch begrenzt ist, wurde im Falle der L¨osungspolymerisation in w¨assriger L¨osung
die Wachstumsrate von acrylischen Monomeren in zwei unterschiedlichen Syste-
men untersucht: die Homopolymerisation von Methacryls¨aure und die Copolyme-
risation von Acryls¨aure mit Acrylamid. Es wurde gezeigt, dass die Polymerisa-
tionsgeschwindigkeit von ionisierten Monomeren im Vergleich zu ihren nicht ge-
ladenen Pendants deutlich geringer ist, dass die Reaktionsgeschwindigkeit jedoch
mit der Menge an Ladungen im Reaktionsmedium zunimmt. Es wurde ein mathe-
matisches Modell angewendet, das die entsprechende Wachstumsgeschwindigkeits-
konstante unter Beru¨cksichtigung einer Abh¨angigkeit der Elektrolytkonzentration
zus¨atzlich zu der gew¨ohnlichen intrinsischen Ausbreitungsrate bestimmt. Das Mo-
dell erwies sich nach Bestimmung der entsprechenden Parameterwerte als sehr
zuverl¨assig. In der Copolymerisationsstudie stimmten die Ergebnisse, die anhand
VII