Polymer Chemistry Blog

Claude St Thomas studied chemistry at the École Normale Supérieure, Université d’État d’Haïti, Port au Prince, Haïti. In 2008, he moved to Mexico where he obtained MSc and PhD degrees in polymer chemistry at the Centro de Investigación en Química Aplicada (CIQA) under the guidance of Dr. Ramiro Guerrero Santos. During his PhD studies, he undertook two research stays at the Laboratory of Chemistry and Processes of Polymerization (LCPP), in Lyon, France under the supervision of Prof Bernadette Charleux and Dr. Franck D’Agosto. He designed a novel dual RAFT/NMP chain transfer agent for a tandem polymerization and investigated its use for preparing the self-assembled nanoparticles. This investigation was awarded with the 2015 Rafael Illescas Frisbie prize from the Mexican Chemistry Society as the best PhD thesis. In the same year, he was promoted as a CONACYT research fellow at CIQA.

His research mainly focuses on the preparation of well-defined multiblock copolymers and the development of novel associative polymers featuring stimuli-responsive groups using reversible deactivation radical polymerization (RDRP) techniques. He is also interested in the rheological properties of polymers for applications in coatings, paints, enhanced oil recovery, and water treatment.

What was your inspiration in becoming a polymer chemist?

In my childhood, I was always fascinated by nature. At the beginning, I dreamed about becoming an agronomist. However, my interest for chemistry started in high school by the teachings from chemistry lecturer Sylvain Jean Desir. There, I understood that chemistry is the basis of life. During my MSc and PhD studies I worked with materials of common and daily use and a special interest for polymer chemistry started rising.

What was the motivation behind your most recent Polymer Chemistry article?

In our research group, scientific contributions related to the preparation of water-soluble copolymers have been previously published under the supervision of Dr. Enrique Javier Jiménez Regalado using free radical polymerization. In 2014, the “Consejo Nacional de Ciencía y Tecnología” (CONACYT, México) started a new program for addressing solutions to national problems, where young researchers were engaged and assigned to specific projects. Since, I started in my current position in 2015 and inspired by the versatility of the RAFT polymerization technique, my current research work focuses on the development of novel pathways for preparing well-defined water-soluble associative copolymers.

Inspired by the RDRP techniques and their feasibility for synthesizing polymeric materials with unprecedented properties, our recent contribution describes a new strategy for preparing environmentally-friendly water-soluble associative copolymers using the RAFT technique.

Which polymer scientist are you most inspired by?

A group of scientists have impacted my career. I appreciate the discipline, rigor and professional achievements of both Prof Bernadette Charleux and Dr. Franck D’Agosto. Fascinated by RDRP techniques, I am also inspired by three experts in RDRP: Prof Craig J. Hawker, Prof. San H. Thang and Prof. Krzysztof Matyjaszewski. Their publications describing processes for synthesizing polymers with specific characteristics might allow the use of these materials in different industrial applications.

Can you name some up and coming researchers who you think will have a big impact on the field of polymer chemistry?

Based on application areas of polymeric materials, it would be difficult to mention researchers who will have a big impact on the field. Notwithstanding, I select Dr. Francesco Picchioni (University of Groningen). His research on the development of chemical materials for application in Enhanced Oil Recovery (EOR) displays great interest and could impact the field. For these researches, I am also impressed by the research works of Dr. Michael F. Cunningham (Queens University) and Sébastien Perrier (University of Warwick)

How do you spend your spare time?

Outside of professional activities, I enjoy spending time with my family (wife and four year-old daughter-Nicole) and visiting natural places. My favorite sport is soccer, so I enjoy playing it with friends. I also enjoy playing guitar and reading about new scientific developments and culture.

What profession would you choose if you weren’t a scientist?

Probably an agronomist due to my passion for natural sciences, because it was my first dream.

Read Claude’s full article now for FREE until the 31st January!

Preparation of hydrophobically modified associating multiblock copolymers via a one-pot aqueous RAFT polymerization

Christina Chai obtained her BSc (Hons) from the University of Canter­bury, Christchurch, New Zealand and her PhD in organic chemistry from the Research School of Chemistry, Australian National University, Canber­ra under the mentorship of the late Professor Athel Beckwith, FRS. Following her PhD, she was awarded a Samuel and Violette Glasstone Research fellowship at the University of Oxford, UK. This was followed by a Faculty position in the Department of Chemis­try, Victoria University of Wellington, NZ (1991-1993) and the Department and Research School of Chemistry, Aus­tralian National University (1994-2004) where she rose to the rank of a Reader. In 2005, Christina moved to Singapore to establish a research programme on synthetic and polymer chemistry at the then newly founded Institute of Chemical and Engineering Sciences, Agency for Science Technology and Research (A*STAR). She returned to a life in academia in 2011 at the Department of Pharmacy, National University of Singapore where she has held many administrative positions. She is currently Professor and the Head of the Department of Pharmacy. Although her major research interest is on bioactive compounds, she moonlights in polymer chemistry with special interest in biomimetic materials.

What was your inspiration in becoming a scientist who works with polymers?

My PhD training was in the area of free radical chemistry with one of the free radical ‘’gods’’, the late Professor Athel Beckwith. At that time, a superb team of chemists in CSIRO Australia had developed the RAFT process which was based on the principles of radical chemistry, and I was fascinated with the numerous possibilities of this process in creating new materials. Although this fascination remained after my PhD studies, I did not have the opportunity to work with polymers until I moved to A*STAR Singapore. I continue to be intrigued with clever ways of designing functional polymers for various applications.

What was the motivation behind your most recent Polymer Chemistry article?

When I first joined NUS, I received a grant that allowed me to work on biomimetic materials, specifically mussel-inspired coatings. I was intrigued with the claims that polydopamine (PDA) is a universal coating material, and was amazed with the reported applications of polydopamine. If one read and believed all the literature, one would imagine that PDA is the answer to all our material needs. As we worked to develop PDA functional coatings, we were hampered by the lack of information on the structure of PDA. We wanted to improve the properties of PDA but how do we improve a mystery material? So we set out to understand the oxidation chemistry of dopamine, and the process of coating and of course, to attempt to elucidate the structure of PDA. I was fortunate that my PhD student at that time, Lyu Qinghua was so obsessed with this mystery that he refused to submit his thesis until he knew the answer. I am not convinced that we have completely solved the mystery (although I did manage to persuade the student to submit his thesis) but I believe that we have made significant progress in the structural elucidation. The answer is just around the corner!

Which polymer scientist are you most inspired by?

In view of my training as a free radical chemist, I was most interested in the ability to control polymer synthesis through living free radical polymerisation methods such as ATRP and RAFT. I personally know Professor San Thang, now of Monash University, who is one of the co-inventors of RAFT, and his life story and his humility despite his successes is one of my inspiration. Professor K. Matyjaszewski, the guru of ATRP and Professor Craig Hawker, with his fascinating designs of functional polymers are also heroes in my eyes.

Can you name some up and coming researchers who you think will have a big impact on the field of polymer chemistry?

Professor Molly Stevens from Imperial College London is a name that comes to mind as her research on materials for biomedical applications will be a game changer.

How do you spend your spare time?

I love reading and travelling. I read fiction and non-fiction for pleasure. My love for travel is not about visiting places of interest but to immerse myself in a different environment and culture.  Although I am an introvert, I am interested in people-watching. People are fascinating subjects for study!

What profession would you choose if you weren’t a scientist?

A doctor, a nun or a scientist – This is what I would say when I was a child when people asked me what I wanted to be when I grew up. As I doubt that I would be religious enough to qualify as a nun, this just leaves being a doctor as my alternate profession that I would choose. However I love being a scientist! I constantly worry about not having enough funds to support my research. My dream is to win the lottery so that I can support my research for the rest of my career…

Is the end in sight for the structural analysis of polydopamine? What important questions remain to be answered?

Yes, I believe that the end is in sight for the structural analysis of polydopamine. I believe that fundamental studies are important if we want to advance the applications. Without knowing the structure, how do we improve the properties of the material? There are still gaps in PDA technology that needs to be addressed. For example, one would need to know how to reproducibly control the thickness and homogeneity of the material; how to reduce the coloration and improve stability…. There is so much that we do not yet know.

Read Christina’s full article now for FREE until the 21st December!

Unravelling the polydopamine mystery: is the end in sight?

Yasuhiro Kohsaka is an Associate Professor in the Research Initiative for Supra-Materials (RISM) and the Faculty of Textile Science and Technology (FTST) at Shinshu University. He started his academic career as a JSPS Research Fellow in 2008 researching supramolecular polymer chemistry under the supervision of Prof. Toshikazu Takata at Tokyo Tech. From 2009 to 2010 he studied as a visiting student under Prof. Timothy Swager at MIT. He received his Ph. D. degree in Engineering at 2011 from Tokyo Tech. He worked as an Assistant Professor in Prof. Tatsuki Kitayama’s group in Graduate School of Engineering Science at Osaka University. In 2015, he moved to FTST at Shinshu University as a Tenure-Track Assistant Professor supported by JST and established his own independent research group. He became an Associate Professor in 2018, and joined the RISM in 2019. Since 2019, he has started a new project on the design of new monomers and polymerization chemistry using synergetic effects of two or more functional groups. His research is always based on pure organic chemistry but proposed with practical application in mind. Therefore, he has interests in both polymer chemistry and material science. He was chosen as one of the Emerging Investigators of 2018 in Polymer Chemistry. Recently, he received a Young Researcher Award from the Society of Polymer Science, Japan (SPSJ) and the Society of Fiber Science and Technology, Japan (SFSTJ).

What was your inspiration in becoming a polymer chemist?

In childhood, my uncle often entertained me with plastic models of airplanes. This experience made me interested in science and technology. However, my favorite subjects were not chemistry but astronomy and earth science. Therefore, I attempted to join the astronomy club in the first year of middle high school, but the atmosphere was not comfortable for me. Then, my friend induced me to join chemistry club, where senior high school students were studying the synthesis of biodegradable plastics. This was my first introduction to polymer chemistry. In 2000, Prof. Hideki Shirakawa won the Nobel Prize in Chemistry for his discovery of conductive polymers. This news had a strong impact on me. I also learned that our daily life was supported by polymer materials, such as plastics, rubbers, fibers and adhesives. Then, I dreamed to develop new functional polymer materials like Prof. Shirakawa and change our life for the better. After that, I am striking out to my dream even now!

What was the motivation behind your most recent Polymer Chemistry article?

This is completely a kind of serendipity. Hemiacetal esters are interesting molecules, as they can be used for various purposes. The formation of a hemiacetal ester bond is reversible and thus it can be applied to dynamic covalent chemistry, while hemiacetal esters can also initiate living cationic polymerization of vinyl ethers. On the other hand, cyclic hemiacetal esters give two different types of polymers, polyesters and poly(hemiacetal ester)s, by ring-opening polymerization (ROP). Therefore, we have interests in the polymerization chemistry of cyclic hemiacetal esters containing polymerizable vinyl groups, as the monomers can undergo both ROP and vinyl polymerization and each product would have the respective potential application according to its residual groups. In our previous paper, therefore, we reported the vinyl polymerization of cyclic hemiacetal esters with acrylate skeleton (J. Polym. Sci. Part A: Polym. Chem. 2016, 54, 955). This monomer contains a hemiacetal ester skeleton, but we are also interested in cyclic ketene acetal esters, which provide hemiacetal ester skeletons by vinyl polymerization. That is, the vinyl polymerization changes the double bond to single bond forming a hemiacetal ester skeleton in the process. For this concept, we sought a cyclic ketene acetal ester in the database and found dehydroaspirin. Therefore, we never aimed to recycle vinyl polymers.

Which polymer scientist are you most inspired by?

Since I am interested in the principles of step-growth polymerization, Prof. Mitsuru Ueda’s (NTU) early papers such as group-selective polycondensation and synthesis of regio-regular polymers always give me a good inspiration. As I conduct a project on ring-opening polymerization, I am also inspired by Prof. Marc Hillmyer (University of Minnesota).

Can you name some up and coming polymer chemists who you think will have a big impact on the field?

I respect Prof. Koji Takagi’s (Nagoya Institute of Technology) energetic activity. He proposes unique and sophisticated approaches in polymer synthesis and collaborates with many young professors to advance his research. His molecular design is simple, but his deep insight and wide viewpoint present the importance of intelligence and dreams of polymer chemistry to our young generations. Speaking about our generations, my best friends, Prof. Hiroaki Imoto (Kyoto Institute of Technology), and Prof. Fumitaka Ishiwari (Tokyo Tech), my junior in school, are the closest but farthest researchers. Their motivation is very pure, and thus, the impacts of the completed results are always strong.

How do you spend your spare time?

As I work away from my family due to business reason, I enjoy driving home to spend the weekend with my wife and children. I like to play with my daughter (four years old) and son (two years old) with my children’s mind. On weekdays, I play and watch Shogi, a Japanese traditional board game like a chess. The way of thinking in Shogi is similar to that in organic chemistry, as the construction and motion of cooperated pieces (atoms) are the keys to winning. I also like to watch sports, particularly baseball and Formula One (F1).

What profession would you choose if you weren’t a chemist?

Earth scientist or astronomer, as they are my first dream in childhood. As it turns out, I am a natural scientist!

Read Yasuhiro’s recent Polymer Chemistry article for FREE until 19th August!

Radical polymerization of ‘dehydroaspirin’ with the formation of a hemiacetal ester skeleton: a hint for recyclable vinyl polymers

Akane Kazama  and  Yasuhiro Kohsaka

A vinyl polymer with a cyclic hemiacetal ester skeleton was synthesized via the radical polymerization of 2-methylene-4H-benzo[d][1,3]dioxin-4-one (MBDO; so-called ‘dehydroaspirin’). This material could be decomposed to acetic acid and salicylic acid (the raw ingredients for MBDO) by acid hydrolysis, and thus has potential as a recyclable vinyl polymer.

About the webwriter

Simon Harrisson is a Chargé de Recherche at the Centre National de la Recherche Scientifique (CNRS), based in the Laboratoire des IMRCP in Toulouse. His research seeks to apply a fundamental understanding of polymerization kinetics and mechanisms to the development of new materials. He is an Advisory Board member for Polymer Chemistry. Follow him on Twitter @polyharrisson

Bumjoon Kim is a Professor in the Department of Chemical and Biomolecular Engineering at KAIST since 2008 where he is appointed as the KAIST Endowed Chair Professor. He completed his doctorate under the guidance of Prof. Edward Kramer at UCSB. Then, he worked with Prof. Jean Fréchet at UC Berkeley. His research interests include development of block copolymer-based functional materials including shape-tunable particles, colorimetric sensors, and design of new electroactive polymers for all-polymer solar cells with high stability. He has published more than 170 peer-reviewed papers and 50 issued/pending patents. He was appointed as the Ewon Assistant Professor at KAIST (2010-2013). Also, he received the KAIST Academic Excellence Award (2015) and Shimgye Science Award (2017), and he was selected as 2013 Young Scientist by the World Economic Forum (DAVOS Forum) and appointed as the KAIST Endowed Chair Professor (2018). He currently serves as an editorial advisory board member of Macromolecules, ACS Macro Letters, Chemistry of Materials (ACS), J. Mater. Chem. A (RSC) and BMC Energy (Springer Nature).

What was your inspiration in becoming a polymer chemist?

I’m not sure what would be the best way to simply describe it. I was educated both as a chemical engineer and a polymer scientist, not a hard core chemist. During my senior year in college, I first learned about polymers in a class named “Introduction to Polymer Engineering” taught by Prof. Kookheon Char at Seoul National University. This course gave me a strong interest in polymer science and motivated me to study polymer science further. Also, I believe I was very fortunate to receive a well-balanced education in both polymer physics and chemistry during my time at graduate school and postdoctoral studies from Profs. Edward Kramer, Craig Hawker (UCSB), and Jean Fréchet (UC Berkeley). These interests and backgrounds have led me to pursue the development of new polymer-based materials that may benefit our lives and society.

What was the motivation behind your most recent Polymer Chemistry article?

Particle shape is one of the most fundamental and essential features that determines the function of polymeric particles. For example, anisotropically shaped particles can exhibit unique optical properties, packing structures, and rheological behaviors. For the last few years, our group has made contributions to the development of the principles dictating the shape of block copolymer (BCP) particles from the evaporative emulsions. For example, I would like to highlight the papers including JACS 2014, 9982; Adv. Funct. Mater. 2018, 1802961; Macromolecules 2019, 1150. This understanding is synergistically combined with a technique called “membrane emulsification” to produce the particles of the same size and shape in a large batch (also see ACS Nano 2017, 2133; Chem. Mater. 2018, 6277), which enables the use of these particles for the various applications described above. In this Polymer Chemistry article, we describe the development of a series of non-spherical Janus particles with interesting cone-shapes. Systematic control of particle shape is achieved by programming the phase-separation of the blend of BCP and newly-synthesized copolymers confined in emulsion droplets. We also have developed a theoretical model to explain the shape of the cone-shaped particles.

Which polymer scientist are you most inspired by?

As I mentioned in the answer to the first question, people who are world-leading polymer scientists as well as great teachers have inspired me and helped a lot to develop my career and do my current research. In particular, I have learned a lot from Prof. Edward Kramer, who was my Ph.D. advisor, on many aspects, such as how to conduct research and attitudes towards students. I believe his patience and inspiration for science have greatly influenced my choice of work as a teacher and professor.

How do you spend your spare time?

I like traveling and walking/driving near the seaside. I spend enough time relaxing and refreshing outside the office. This helps me to think more clearly. Also, I enjoy spending time with my 7-year-old daughter, Jaeyeon.

What profession would you choose if you weren’t a chemist?

I would like to be a teacher or a cook. Since I like teaching, I would spend time teaching young students if I were not a chemist. Also, I like cooking, so I think becoming a cook can be a great choice for me. I think there are many connections between cooking and doing experiments.

Read his Polymer Chemistry article for FREE until 15th July

Shape control of nanostructured cone-shaped particles by tuning the blend morphology of A-b-B diblock copolymers and C-type copolymers within emulsion droplets 

Eun Ji Kim,  Jae Man Shin,  YongJoo Kim,  Kang Hee Ku,  Hongseok Yun  and  Bumjoon J. Kim

Block copolymers (BCPs) under colloidal confinement can provide an effective route to produce non-spherical particles. However, the resulting structures are typically limited to spheroids, and it remains challenging to achieve a higher level of control in the particle shape with different symmetries. Herein, we exploit the blend of BCPs and statistical copolymers (sCPs) within emulsion droplets to develop a series of particles with different symmetries (i.e. Janus-sphere and cone-shaped particles). The particle shape is tunable by controlling the phase behavior of the polymer blend consisting of a poly(styrene-block-1,4-butadiene) (PS-b-PB) BCP and a poly(methylmethacrylate-statistical-(4-acryloylbenzophenone)) (P(MMA-stat-4ABP)) sCP. A key strategy for controlling the phase separation of the polymer blend is to systematically tune the incompatibility between the BCP and sCP by varying the composition of the sCPs (ϕ_4ABP, mole fraction of 4ABP). As a result, a sequential morphological transition from a prolate ellipsoid, to a Janus-sphere, to a cone-shaped particle is observed with the increase of ϕ_4ABP. We further demonstrate that the shape-anisotropy of cone-shaped particles can be tailored by controlling the particle size and the Janusity, which is supported by quantitative calculation of the particle shape-anisotropy from the theoretical model. Also, the importance of the shape control of the cone-shaped particles with high uniformity in a batch is demonstrated by investigating their coating properties, in which the deposited coating pattern is a strong function of the shape-anisotropy of the particles.

About the webwriters

Simon Harrisson is a Chargé de Recherche at the Centre National de la Recherche Scientifique (CNRS), based in the Laboratoire des IMRCP in Toulouse. His research seeks to apply a fundamental understanding of polymerization kinetics and mechanisms to the development of new materials. He is an Advisory Board member for Polymer Chemistry. Follow him on Twitter @polyharrisson

Professor Athina Anastasaki is an Editorial Board Member and a Web Writer for Polymer Chemistry. In January 2019 she joined the Materials Department of ETH Zurich as an Assistant Professor to establish her independent research group.

Sandra Schlögl studied Technical Chemistry at Graz University of Technology (Austria), where she obtained her Master degree in 2006. In 2006, she joined the Polymer Competence Center Leoben (PCCL), which is the leading ‘Center of Excellence’ for cooperative research in the area of polymer engineering and sciences in Austria. Two years later, she received her Ph.D. degree in Polymer Chemistry from Graz University of Technology. She was a visiting scientist at Politecnico di Torino (Italy) in the group of Prof. Marco Sangermano in 2016, and finished her habilitation (post-doctoral lecturing qualification) in Macromolecular Chemistry in 2017. Currently, she heads the ‘Chemistry of Functional Polymers’ division at PCCL. In addition, she is a lecturer at Montanuniversitaet Leoben (Austria) teaching courses at an MSc level in polymer photochemistry and in stimuli-responsive polymer materials. Her research centers on stimuli-responsive polymers, dynamic networks, elastomer chemistry and photochemistry in polymers. She is author of more than 50 peer-reviewed publications (Scopus H-index of 10), inventor of 11 patents (national and international) and has received several awards for her research (e.g. Paul Dufour Award in 2015, EARTO Innovation Award in 2016).

What was your inspiration in becoming a polymer chemist?

My career as a polymer chemist was not planned. In school, I always had a talent for natural-science subjects and back then, as today, I was intrigued by biological and biochemical processes of the human body. Obviously, my first plan was to study medicine and I even took Latin courses at school. However, during my voluntary work in the health care sector, I recognized that medicine is interesting in theory but hard to carry out in practice. I started to rethink my career plans, which led to my decision to study chemistry. The curriculum of the technical chemistry studies sounded promising since it also contained biochemistry, which was not so far away from medicine. However, during my studies I developed a favorite research activity: creating functional polymers. I took inspiring lectures and lab courses in polymer photochemistry, where I learned versatile and creative routes to change material properties on demand. Since then, the chemistry of polymers has me hooked.

What was the motivation behind your recent Polymer Chemistry article?

A strong focus of my working group is the synthesis of stimuli-responsive polymers, by introducing photocleavable chromophores and photoreversible binding motifs into polymer structures. These polymers change their material characteristics in response to external stimuli (such as light and temperature), which is used for numerous applications such as self-healable materials, reversible adhesives or switchable micropatterns.

Since several years, I have successfully cooperated with Marco Sangermano and Ignazio Roppolo from Politecnico di Torino on several research topics, joining the expertise of our working groups. Ignazio is not only a dedicated soccer player but also watches documentaries in his spare time. He was fascinated by the ability of desert beetles to collect humidity and transport water droplets across their skin. We discussed the topic and the idea was born to transfer the concept to photopolymer materials. Mimicking nature with synthetic materials for controlled water transport is not new, but the majority of the reported concepts rely on inorganic materials requiring time consuming and elaborate sample preparation techniques. With our recent Polymer Chemistry article, we succeeded to generate multi-gradients on polymer surfaces simply by light exposure. We introduced both a wettability gradient and a Laplace pressure gradient by a localized light-induced switching of the polarity, which is required to drive a water droplet across the photopolymer surface in a controlled way. This opens the path towards a precise movement of individual or multiple droplets on surfaces with complex topology and tailored surface polarity.

Which polymer scientist are you most inspired by?

In my field of research I am most inspired by the pioneering work of two scientists: Christopher N. Bowman (University of Colorado Boulder) and Christopher Barner-Kowollik (Queensland University of Technology). They are at the forefront of research in polymer photochemistry and their research is an important driving force for the development of new photopolymers with fascinating properties.

Can you name some up and coming polymer chemists who you think will have big impact on the field?

In my opinion, the research work of Miriam M. Unterlass (Vienna University of Technology) on hydrothermal polymerization has the potential to greatly influence future synthesis routes in polymer chemistry. Her research focuses on geomimetics, which takes inspiration from nature for generating novel synthetic materials under high pressure and with water as solvent. In one-pot reactions with low energy consumption, she is able to synthesis a great variety of materials involving polymers, dyes or inorganic-organic hybrids. I think that Miriam’s research has a great potential for the ‘green’ synthesis of new and traditional high-performance polymers; not only on a lab but also on an industrial scale.

How do you spend your spare time?

I am fond of outdoor sports, which are a good balance to my professional life, which over the past years is less and less taking place in the chemical lab but more in the office. I am a hobby racing cyclist, who tries to avoid the mountain areas, which is not an easy task in Austria and I do some running in between. I also enjoy spending time with my family and friends and in case of bad weather I like reading novels from different genres.

What profession would you choose if you weren’t a chemist?

I would choose again a profession in science since I can only agree with Madame Marie Curie that ‘science has great beauty’.

Read her Polymer Chemistry article for FREE until June 10th!

Directed motion of water droplets on multi-gradient photopolymer surfaces
E. Rossegger,  D. Hennen, T. Griesser, I. Roppolo  and  S. Schlögl

The present work highlights the controlled directional movement of water droplets across a photopolymer surface. The movement is propelled by multi-gradients including a wettability gradient and a Laplace pressure gradient. Both gradients are conveniently adjusted by light employing a photoresponsive thiol–yne photopolymer. o-Nitrobenzyl alcohol derivatives with terminal alkyne groups are synthetized and cured across di- and tri-functional thiols upon visible light exposure. The wettability gradient is generated in a subsequent step involving an asymmetrical irradiation of the polymer surface with light in the UV-A spectral region. Polar groups are formed in the exposed areas due to the photocleavage of the chromophore and photo-oxidation reactions (upon prolonged UV exposure in air). The wettability rises with increasing exposure dose and gradient surfaces are prepared with static water contact angles ranging from 97 to 19°. By simultaneously inscribing the wettability gradient in wedge-shaped patterns, a Laplace pressure gradient is realized on the photopolymer surface, which can be easily tailored by the size and the angle of the wedge. The combination of both gradients enables a rapid and directed movement of water droplets (2 μL droplet) over a reasonable distance (up to 10 mm). Due to the high adhesion of the photopolymer surface, the droplet can be driven in a controlled way, even if the surface is inclined (20°) or turned upside down.

About the Web writer

Simon Harrisson is a Chargé de Recherche at the Centre National de la Recherche Scientifique (CNRS), based in the Laboratoire des IMRCP in Toulouse. His research seeks to apply a fundamental understanding of polymerization kinetics and mechanisms to the development of new materials. He is an Advisory Board member for Polymer Chemistry. Follow him on Twitter @polyharrisson