Archive for August, 2015

Author of the Month: Dr Daniel Klinger

Daniel obtained his degree in chemistry from the Johannes Gutenberg University in Mainz, Germany. During his diploma studies under the guidance of Prof. Dr. Patrick Theato, he worked on the development of photo-switchable block copolymers using controlled radical polymerization methods. He then moved to the group of Katharina Landfester at the Max Planck Institute for Polymer Research in Mainz where he received his PhD at the end of 2011. During this time he focused on the development of responsive microgels and polymeric nanoparticles for enzymatic and light-triggered release applications. In, early 2012, Daniel joined the group of Craig J. Hawker at the University of California in Santa Barbara as a postdoctoral researcher and started working on surfactant-directed block copolymer self-assembly in nanoparticles.

In his current position as project leader in the Materials Research Laboratory at UCSB, he combines the areas of block copolymer self-assembly, with his existing experience in the fields of stimuli-responsive materials and colloidal chemistry. He currently focuses on the development of functional nanomaterials from the controlled assembly of tailor-made polymeric building blocks. Among other areas, he is interested in phase-separated block copolymer nanoparticles, stimuli-responsive micro- and nano gels and new polymers and composite materials for applications in photonics, optoelectronics and thermal conductors.

What was your inspiration of becoming a chemist?

From early on, I was always interested in understanding how things around me work and constantly asked the questions, “Why is it like this?” and “How come it does that?” It was my father – a chemistry teacher – who first showed me that all these interesting phenomena could be explained by the interaction of atoms and molecules. I became hooked on the subject in high school when I learned that these physical and chemical principles could be used to develop entirely new materials of my own design. It is this process of developing new materials by combining a theoretical understanding with the handicraft of an actual experiment that still excites me and drives my research.  The ability to transform an abstract idea on paper into a reality in the lab is highly rewarding to me.

What was the motivation to write your Polymer Chemistry article?

To me, stimuli-responsive microgels have long been an interesting class of materials. Adjusting the swelling and degradation profiles via macromolecular design allows for precise tuning of their loading and release behavior. However, the utilization and efficiency of such nanoparticles in actual biomedical applications crucially depends on various structural parameters such as surface chemistry, size and size distribution. Since investigations on new responsive particles normally come with variations in these factors, accurately comparing the biological efficiency of different approaches is difficult. To overcome this limitation, I wanted to develop a synthetic platform that could investigate different response mechanisms while keeping the structural and morphological parameters constant, and the approach presented here is a first step towards realizing this goal.

Why did you choose Polymer Chemistry to publish your work?

Polymer Chemistry is a great platform for the rapid publication of studies that are not only focusing on macromolecular synthesis but also combine new polymeric materials with a variety of different research fields and applications. Since our presented research is based on combining polymer chemistry with the area of functional colloids, the interdisciplinary character of the journal makes our work accessible to a broad readership and thereby enhances its exposure.

In which upcoming conferences may our readers meet you?

Most likely, I will attend the fall ACS meeting in Boston 2015.

How do you spend your spare times?

I really like travelling and exploring new countries, cultures and foods around the world. I am especially happy if I am able to combine this with spending time in nature. I love being active outdoors and enjoy hiking, rock climbing and camping in the wilderness where simple things like sitting around the campfire can be the best reward after a long day.

Which profession would you choose if you were not a scientist?

Being a chemist, I enjoy mixing things together to make new and interesting products. If I were not a scientist, I would combine this excitement with my passion for food to become a chef. I am just not sure whether a lot of people would enjoy these “experiments”.


A robust platform for functional microgels via thiol–ene chemistry with reactive polyether-based nanoparticles

Carolin Fleischmann,   Jeffrey Gopez,   Pontus Lundberg,   Helmut Ritter,   Kato L. Killops,   Craig J. Hawker and   Daniel Klinger

We herein report the development of crosslinked polyether particles as a reactive platform for the preparation of functional microgels. Thiol–ene crosslinking of poly(allyl glycidyl ether) in miniemulsion droplets – stabilized by a surface active, bio-compatible polyethylene glycol block copolymer – resulted in colloidal gels with a PEG corona and an inner polymeric network containing reactive allyl units. The stability of the allyl groups allows the microgels to be purified and stored before a second, subsequent thiol–ene functionalization step allows a wide variety of pH- and chemically-responsive groups to be introduced into the nanoparticles. The facile nature of this synthetic platform enables the preparation of microgel libraries that are responsive to different triggers but are characterized by the same size distribution, surface functionality, and crosslinking density. In addition, the utilization of a crosslinker containing cleavable ester groups renders the resulting hydrogel particles degradable at elevated pH or in the presence of esterase under physiological conditions.


Cyrille Boyer is a guest web-writer for Polymer Chemistry. He is currently an associate professor and an ARC-Future Fellow in the School of Chemical Engineering, University of New South Wales (Australia) and deputy director of the Australian Centre for NanoMedicine.


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Author of the Month: Dr. Patrick Lacroix-Desmazes

Dr. Patrick Lacroix-Desmazes graduated in 1992 from the National School of Chemistry of Montpellier, France, and received a Master degree in Polymer Science from the University of Montpellier. He obtained his PhD degree in 1996 from the University Claude-Bernard Lyon I, under the supervision of Professor Alain Guyot in collaboration with Elf Atochem and in the frame of a European program on reactive surfactants, on the use of macromonomers as stabilizers in dispersion polymerization in polar media. After a postdoctoral research in 1997 on suspension polymerization with inorganic stabilizers at BP Chemicals in Wingles, he joined CNRS as a junior scientist working with Professor Bernard Boutevin. In 1999, he developed RITP, a promising method for controlled/living radical polymerization. He received his Habilitation Degree in 2004. He was awarded the 2004 Innovative Research ADER Award (Association for the development of Education and Research) in collaboration with Solvay. In 2009, he was distinguished as a researcher laureate from Languedoc-Roussillon and the same year he was promoted CNRS research director. Currently, he is the head of the team Engineering Macromolecular Architectures (IAM) at the Institute Charles Gerhardt in Montpellier. He is deputy president of the French Polymer Group association (GFP) and active member of the French Chemical Society (SCF). His research interests cover the mechanisms and kinetics of controlled radical polymerizations (photoiniferters, NMP, ATRP, RAFT, ITP, RITP), including in dispersed media (emulsion, dispersion, suspension polymerization), the self-assembly of polymers, the bottom-up elaboration of hybrid materials as well as the synthesis and use of polymers in liquid or supercritical carbon dioxide for the development of clean processes in unconventional media.

Link to my research group’s website: http://iam.icgm.fr/

What was your inspiration in becoming a chemist?

When I was very young, my first wish was to become a novelist. Then, during my studies I became more and more interested by sciences and my dream was to become aerospace engineer or something related to the exploration of universe! But I was not brilliant enough in math to reach this goal. And, as I also appreciated chemistry and all the mystery about it from alchemy to modern chemistry, I found that becoming chemist could be a good way to satisfy my thirst for creation. Researcher in chemistry is a great job: I like it not only on a scientific point of view but also because it is an excellent way to make new friends all over the world and share our cultures.

What was the motivation to write your Polymer Chemistry article?

We have been working on double hydrophilic block copolymers (DHBC) since a few years and with some colleagues of our institute we have shown that such copolymers could be nicely used as structure-directing agents in the elaboration of hybrid mesoporous silica materials (paper here). In the present article, we wanted to detail the synthesis of such copolymers and to show how a platform of DHBC with different characteristics (cationic, anionic, pH- or T-stimuli responsive) could be efficiently produced. Many papers appear in the literature on this topic but quite few are giving and discussing the very details that make the synthesis more or less challenging, so we tried to emphasize on such details.

Why did you choose Polymer Chemistry to publish your work?

Polymer Chemistry is a journal with a good audience and fast dissemination and the reviewing process is usually constructive. For this article, we really took our time to fully answer the comments of the referees. This journal is a leading one in chemistry and the editorial and production team is well organized.

In which upcoming conferences may our readers meet you?

My next conference will probably be the 3rd International Symposium on Green Chemistry to be held in La Rochelle on May 3-7 2015. I will present our latest results on polymer-assisted clean processes in supercritical carbon dioxide.

How do you spend your spare times?

I like hiking in general and in the mountains when I have enough time, contemplating nature, far from the rushing modern life. I also enjoy swimming, running and biking with my 14 and 16 years old girls. I love travelling and discovering new countries and share other cultures with my family.

Which profession would you choose if you were not a scientist?

I think I would create a new type of job: itinerant teacher. Instead of the students coming to the teacher, the teacher would visit the students worldwide to share the knowledge and cultures.


Asymmetric neutral, cationic and anionic PEO-based double-hydrophilic block copolymers (DHBCs): synthesis and reversible micellization triggered by temperature or pH

Maël Bathfield,   Jérôme Warnant,   Corine Gérardin and  Patrick Lacroix-Desmazes

The syntheses of three poly(ethylene oxide)-based (PEO) double-hydrophilic block copolymers (DHBCs) of different second block nature (thermosensitive poly(N-isopropylacrylamide) (PNIPAM) block, anionic poly(vinylbenzyl phosphonic di-acid) block, and cationic poly(vinylbenzyl triethyl ammonium chloride) block) are described. The synthesis strategy depends on the synthesis of a single 5kD-PEO-based macro-chain transfer agent that is able to control the RAFT polymerizations of various functional monomers. Low molecular weights of the second block were targeted to obtain asymmetric structures for the DHBCs. Their ability to form micelles under appropriate conditions (specified temperature, pH and nature of the auxiliary of micellization) and the reversibility of the micellization process were checked. Finally, a nanostructured hybrid silica material was obtained using the PNIPAM-based copolymer as a structure-directing agent (SDA), which yielded well-organized mesoporous silica after template removal.


Cyrille Boyer is a guest web-writer for Polymer Chemistry. He is currently an associate professor and an ARC-Future Fellow in the School of Chemical Engineering, University of New South Wales (Australia) and deputy director of the Australian Centre for NanoMedicine.


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Introducing our newest Advisory Board member: Priyadarsi De

We are delighted to announce that Dr Priyadarsi De (Indian Institute of Science Education and Research Kolkata, India) has joined the Advisory Board of Polymer Chemistry.

Dr. Priyadarsi De is currently Associate Professor in the Department of Chemical Sciences in the Indian Institute of Science Education and Research Kolkata (IISER-K). He has held positions at University of Massachusetts Lowell, USA, where he worked as a post-doctoral fellow in the group of Professor Rudolf Faust, and in Southern Methodist University (Dallas, USA) with Professor Brent Sumerlin. He has also spent time in industry, as a Distinguished Scientist at PhaseRx Pharmaceuticals, Seattle, USA.

His research interests include RAFT polymerization of amino acid and fatty acid based monomers, polymeric-inorganic hybrid nanomaterials, polymeric polyelectrolytes, cross-linked polymeric hydrogels and organogels, and weak-link polymers such as polyperoxides and polysulfides.

See some of Priyadarsi’s recent Polymer Chemistry papers:

Polymerization-induced self-assembly driving chiral nanostructured materials
Kamal Bauri, Amal Narayanan, Ujjal Haldar and Priyadarsi De
Polym. Chem., 2015,6, 6152-6162

POSS-induced enhancement of mechanical strength in RAFT-made thermoresponsive hydrogels
Ujjal Haldar, Mridula Nandi, Binoy Maiti and Priyadarsi De
Polym. Chem., 2015,6, 5077-5085

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Paper of the month: Efficiency assessment of single unit monomer insertion reactions for monomer sequence control: kinetic simulations and experimental observations

Haven et al. describe the efficiency of single monomer insertion via both kinetic simulations and experimental observations.

So-called sequence controlled materials have recently received considerable interest due to the precise and freely selectable order of monomers in a monodisperse chain. Such materials exhibit the precision of the peptides in all aspects and differentiate this approach from the synthesis of multiblock copolymers, where a significant dispersity (albeit <1.10 in many occasions) is displayed. Herein, Junkers and co-workers provide an in depth elucidation of the crucial factors that should be taken into account when performing single unit monomer insertion (SUMI) reactions. Both modelling and experimental data confirm that isolated yields of each insertion are comparatively low when going beyond the third monomer addition and as such, even lower yields must be expected for further monomer insertions. Kinetic simulations have shown that most reaction conditions play only a minor role for the success of the insertions and thus, a wide range of conditions can be applied for the synthesis of such materials. Moreover, the effect of the chain-length dependency on the SUMI reactions has also been critically evaluated. Importantly, the carefully optimized conditions obtained from microreactor experiments and kinetic modelling has been subsequently applied to upscale the SUMI reactions in a mesoflow reactor. Although the facile access to such materials demonstrates the pathway towards future developments in the synthesis of longer sequence controlled oligomers, the challenge remains whether oligomers with chain length above 5 will also be available

Tips/comments directly from the authors:

  1. For Single Unit Monomer Insertion reactions (SUMIs), product yield optimization is by stopping the reaction after exactly one monomer equivalent consumption. The reaction rate, thus radical initiator concentration, temperature and overall monomer conversions play a minor role; SUMIs can thus be performed within few minutes.
  2. To study the yield of a SUMI reaction, one needs to distinguish isolated yield from the yield in the crude product mixture. Practically, isolated yields are very dependent on the efficiency of the product isolation method. Yields from the crude can be obtained by careful calibration of mass spectra intensities.
  3. As long as monomers with more or less equal reactivities are chosen, a yield of ~50% is the theoretical maximum.
  4. Evaluation of experimental yields under optimized conditions show that the yield decreases with increasing length of the sequence-defined oligomers. This effect is attributed to a strong chain-length dependency of the monomer propagation rate coefficients.
  5. For upscaling of SUMI reactions, micro- and mesoflow reactors offer the perfect solution.

Efficiency assessment of single unit monomer insertion reactions for monomer sequence control: kinetic simulations and experimental observations, by J.J. Haven, J. Vandenbergh, R. Kurita, J. Gruber and T. Junkers, Polym. Chem., 2015, 6, 5752-5765.


Dr. Athina Anastasaki is a Web Writer for Polymer Chemistry. She is currently a Warwick (UK)/ Monash (Australia) research fellow working under the Monash Alliance. Visit http://haddleton.org/group-members for more information.

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