Archive for July, 2012

Paper of the Week: Stimuli-responsive cholesterol conjugated polymers

Graphical abstract: Synthesis, self-assembly and stimuli responsive properties of cholesterol conjugated polymers

Reversible addition–fragmentation chain transfer (RAFT) polymerization was used to generate well-defined pH-responsive biofunctional polymers as potential ‘smart’ gene delivery systems. A series of five poly(dimethylamino ethyl methacrylate-co-cholesteryl methacrylate) P(DMAEMA-co-CMA) statistical copolymers, with similar molecular weights and varying cholesterol content, were prepared. The syntheses, compositions and molecular weight distributions for P(DMAEMA-co-CMA) were monitored by nuclear magnetic resonance (NMR), solid-state NMR and gel permeation chromatography (GPC) evidencing well-defined polymeric structures with narrow polydispersities. Aqueous solution properties of the copolymers were investigated using turbidimetry and light scattering to determine hydrodynamic diameters and zeta potentials associated with the phase transition behaviour of P(DMAEMA-co-CMA) copolymers. UV-Visible spectroscopy was used to investigate the pH-responsive behaviour of copolymers. Hydrodynamic radii were measured in the range 10–30 nm (pH, temperature dependent) by dynamic light scattering (DLS). Charge studies indicated that P(DMAEMA-co-CMA) polymers have an overall cationic charge, mediated by pH. Potentiometric studies revealed that the buffering capacity and pKa values of polymers were dependent on cholesterol content as well as on cationic charge. The buffering capacity increased with increasing charge ratio, overall demonstrating transitions in the pH endosomal region for all five copolymeric structures. Cell viability assay showed that the copolymers displayed increasing cytotoxicity with decreasing number of cholesterol moieties. These preliminary results show the potential of these well-defined P(DMAEMA-co-CMA) polymers as in vitro siRNA delivery agents.

Synthesis, self-assembly and stimuli responsive properties of cholesterol conjugated polymers by Sema Sevimli,  Sharon Sagnella,  Maria Kavallaris,  Volga Bulmus and Thomas P. Davis Polym. Chem. 2012, 3, 2057-2069.

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Author of the Week: Prof. Shiao-Wei Kuo

Shiao-Wei Kuo received his BSc degree in Chemical Engineering from National Chung-Hsing University in 1998 and Ph.D degree in Applied Chemistry from National Chiao-Tung University in Taiwan in 2002 where he worked with Prof. Feng-Chih Chang. He continued his research work at Chiao-Tung University as a postdoctoral researcher during 2002-2007. From September 2005 to April 2006, he was also a postdoctoral researcher with Prof. Stephen Z. D. Cheng at the University of Akron in USA. He joined Department of Materials and Optoelectronic Science, National Sun Yat-Sen University in Taiwan as an assistant professor in 2007 and was promoted to associate professor in 2010. He has published ca. 160 research papers, 3 review articles and 3 book chapters. His research interests include polymer interactions, supramolecular chemistry, self-assembly nanostructures, mesoporous materials, POSS nanocomposites, polymer bioconjugates, and low surface free energy materials.

For more information see here: http://www.mse.nsysu.edu.tw/people/bio.php?PID=23

What was your inspiration in becoming a chemist?

When I was a high school student, I was interested in mathematics. Chemistry is difficult to attract me since we only learn the chemistry knowledge from the textbook and lack the hands-on chemical experiment at that moment. However, I had the highest score in chemistry for my university entrance exam held in Taiwan that year and I was assigned to department of chemical engineering in Chung-Hsing University. During that period, I discovered that polymer research is fascinating work and the hands-on experience in a laboratory setting provided me with numerous opportunities to corroborate what I had learned from textbook and then extend that knowledge to an independent search for innovative solutions. At Chiao-Tung University, the excellent research environment and abundant academic resources also enhanced my research capabilities and equipped me with the competence to fully realize my research aspirations in polymer chemistry, including the synthetic methods such as anionic polymerization, controlled radical living polymerization, and ring-opening polymerization.

What was the motivation behind the research in your recent Polymer Chemistry paper?(DOI:10.1039/C2PY20197F)

My Ph.D. thesis was focused on the hydrogen bonding interaction in polymer blend systems. At the end of postdoctoral research, my research interest was changed to self-assembly supramolecular structure of diblock copolymer mixture such as poly(styrene-b-vinyl phenol) diblock copolymer blending with poly(4-vinyl pyridine) or poly(methyl methacrylate) through hydrogen bonding interaction. In general, these interactions have been formed through single-site hydrogen bonding (e.g., hydroxyl, carboxyl, pyridyl, or ether groups), but they are relatively weaker than the complementary multiple hydrogen bonding interactions formed in DNA-like complexes. As a result, we wished to mimic DNA-like interactions to synthesize heteronucleobase (thymine)-containing diblock copolymers by using a combination of nitroxide-mediated radical polymerization and click chemistry, which we then blended with the adenine-based molecules to form self-assembly supramolecular structures, through strong complementary multiple hydrogen bonds, with different length scales.

Why did you choose Polymer Chemistry to publish your work?

From the website, the scope of Polymer Chemistry including novel properties and characterization of polymers, synthesis and application of polymer bioconjugates, supramolecular polymer chemistry, and polymer nanocomposites is very close to my recent research interest. It is natural for me to publish our research papers in this journal and we also publish several papers in this journal in this year due to broad readership and fast review process and publication. Most importantly, Polymer Chemistry is an excellent journal with high quality and impact manuscript in polymer science.

In which upcoming conferences may our readers meet you?

I will attend the Symposium about liquid crystal and supramolecular self-assembly structure in Xiangtan City in China during August 26-29, and the 2nd Symposium on Innovative Polymers for Controlled Delivery in Suzhou, in China during September 11-14.

How do you spend your spare times?

I have two small children and I spend almost my free time to take care of my daughter and son. I like travelling with my family and watching sport games on TV, especially in baseball and basketball when I have free time.

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

For hundreds of years and countless generations, people in my family have been farmers or fishermen in my hometown. My father and my brother both are still fishermen now and maybe I will enjoy this job to get along with the sea. However, I like to teach and to do research now and I think that it is the best choice for me at this moment.

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Introducing Brent Sumerlin as a new Polymer Chemistry Associate Editor

Brent S. SumerlinPolymer Chemistry is delighted to welcome Professor Brent S. Sumerlin as an Associate Editor.

“It is an honor to become an Associate Editor for Polymer Chemistry. Since it’s original launch in 2010, I have been an avid supporter of the journal in various capacities, most importantly as an author. The rapid success of the journal and its acceptance by polymer chemists worldwide is exciting. The editors, Editorial Board, Editorial Advisory Board, authors, and referees have worked hard to make this one of the top polymer journals. I look forward to contributing to the continued success and growth of Polymer Chemistry in the years to come.”

If you’d like to learn more about Professor Sumerlin’s own research you can find a few of his recent papers below. He’s also been featured as an ‘Author of the Week’ in 2011 and in video interview in earlier in the year.

Recent papers:

Professor Brent S. Sumerlin, Associate Editor Prof. Brent S. Sumerlin graduated with a B.S. from North Carolina State University (1998) and obtained a Ph.D. in Polymer Science and Engineering at the University of Southern Mississippi (2003) under the direction of Prof. Charles L. McCormick. After serving as a Visiting Assistant Professor at Carnegie Mellon University under the direction of Prof. Krzysztof Matyjaszewski (2003-2005), he joined the Department of Chemistry at Southern Methodist University (Dallas, Texas, USA) as an assistant professor in 2005 and was promoted to associate professor in 2009. Prof. Sumerlin joined the Department of Chemistry, the George and Josephine Butler Polymer Research Laboratory, and the Center for Macromolecular Science and Engineering at the University of Florida as an associate professor in the fall of 2012. He has received several awards, including an Oak Ridge Associated Universities Ralph E. Powe Award (2007), an NSF CAREER Award (2009), an ACS Leadership Development Award (2010), and an Alfred P. Sloan Research Fellowship (2010). He is a member of the editorial advisory boards for several journals and is now an Associate Editor of Polymer Chemistry. Current research in his group involves the synthesis of functional macromolecules, responsive polymer systems, polymer-protein bioconjugates, and dynamic covalent macromolecular assemblies.

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Paper of the Week: Hyperbranched polythioether-ynes by thiol-halogen click-like coupling and thiol-yne click polymerization

Fast and scalable production of hyperbranched polythioether-ynes was achieved by applying sequential click chemistry (SCC) via couple-monomer methodology (CMM). As a typical example, thiol-halogen click-like reaction employing strong base, KOH and thiol-yne click reaction via UV irradiation were used for precursor preparation and polymerization, respectively. Two series of hyperbranched polythioether-ynes employing two kinds of di-thiols with different reactivity have been prepared within 10 h and characterized with 1H NMR spectroscopy and gel permeation chromatography. The hyperbranched polymers (HPs) derived from 1,6-hexanedithiol reached high weight-average molecular weight (Mw) of 230500, high weight-average degree of polymerization (DPw) of 1224 and high degree of branching (DB) of 0.82–0.68. Postmodification of abundant alkyne terminal groups afford HPs with a greatly enhanced DB of 0.96. Heat-initiated polymerization was also attempted. The present study clearly demonstrates the robustness of application of SCC technique in the CMM strategy for fast, scalable preparation of multifunctional HPs.

Fast and scalable production of hyperbranched polythioether-ynes by a combination of thiol-halogen click-like coupling and thiol-yne click polymerization by Jin Han, Bo Zhao, Aijin Tang, Yanqin Gao and Chao Gao Polym. Chem., 2012, 3, 1918-1925

To keep up-to-date with all the latest research, sign up for the journal’s e-alerts or RSS feeds or follow Polymer Chemistryon Twitter or Facebook.

 

 

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Author of the Week: Wantai Yang

Dr Wantai Yang received his bachelor’s degree from Tsinghua University in China in 1982 and MS degree in 1985 from Beijing Institute of Chemical Technology (presently known as Beijing University of Chemical Technology, BUCT), and Ph.D. degree from Royal Institute of Technology in Sweden in 1996. He started his research career in 1985 at BUCT where he is currently a Professor of Polymer Chemistry and serves as Dean of College of Materials Sci. & Eng. He has published more than 290 peer-reviewed papers in international journals and filed over 15 patents. He also has been an invited speaker and/or chairman at more than 20 international meetings. Professor Yang has received many honors and awards for his outstanding research achievements, including Natural Science Award of Ministry of Education (2009), China National Science Fund for Distinguished Young Scholar (1999) and Chair Professor of Cheung Kong Scholars Programme (2001). He is the Vice-President of Chinese Society for Imaging Science and Technology (CSIST), and members of the editorial board of several journals including Biomacromolecules, Chinese Journal of Polymer Science, Membrane Sci. and Tech., Process Engineering and Thermosetting Resin.

His research interest focuses on basic/fundamental chemistry for polymer synthesis and modification. At present his main directions include photopolymerization, controlled/living polymerization, heterogeneous polymerization, new chemistry for surface modification of  organic polymeric material.

For more information, see: http://www.cmse1.buct.edu.cn/ywt/cncss/yjly.asp

What was your inspiration in becoming a chemist?

There are two reasons for me to become a chemist. One is the strong will to know what is polymer science, which seems so curious and mysterious to me before I went to university. Another is due to my high school teacher, who is a very kind person. When I knew he graduated from major of Polymer Science of Tsinghua University just before applying to university, I firmly determined to study polymer science.

What was the motivation to write this article? (DOI: 10.1039/C2PY20117H)

As we known, although the developments in the past 20 years have involved a series of breakthroughs in the living radical polymerization (LRP) field, we have to face the fact that due to inherent drawbacks for each method, even abundant efforts have been endeavored, large-scale industrial applications of LRP remain a big challenge, and a possible alternative solution is return to full organic system. We have presented the first example of living radical graft polymerization on the surface of polymeric materials by use of benzophenone (BP), xanthone and 9-fluorenone as graft polymerization photoinitiators (Macromolecules, 1996, 29, 3308). Therefore, one motivation of this work is to direct the similar reaction into bulk and solution polymerization system to open/explore a novel controlled/living radical polymerization. While another motivation, we hope, our work could attract more chemists pay attention to full organic, especially to this kind of system with cycloketone compounds.

Why did you choose Polymer Chemistry to publish your work?

Although it is a new journal, Polymer Chemistry has become one of top journal in polymer science. It is our great pleasure to publish our work in this journal due to its good visibility.

In which upcoming conferences may our readers meet you?

I will attend the 20th Annual International Conference on Composites or Nano Engineering, ICCE-20, July 22-28, 2012 in Beijing and the 244th ACS National Meeting in Philadelphia on 19–23 August 2012.

How do you spend your spare times?

I enjoy swimming, sing songs, or listen to music.

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

I would probably be a farmer or architect.

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Paper of the Week: Poly(ethylene) brushes grafted to silicon substrates

A poly(glycidyl methacrylate) (PGMA) synthesized by RAFT polymerization was spin-coated onto a silicon substrate to yield, after annealing and rinsing unreacted chains, covalently attached epoxy-containing PGMA pseudo-brushes. A tailor-made ω-amino-poly(ethylene) (Mn = 1040 g mol−1, PDI = 1.3) was then grafted in melt at 130 °C for 24 h by reaction between amine chain-ends and surface-tethered epoxy groups. After discarding unreacted poly(ethylene) chains by sonication and Soxhlet rinsing, the resulting poly(ethylene) brushes were characterized by scanning probe microscopy, water contact angle and neutron reflectivity measurements. The grafting of poly(ethylene) brushes to silicon substrates has thus been demonstrated for the first time and resulted in nanostructured grafted layers with homogeneous surface coverage.

Poly(ethylene) brushes grafted to silicon substrates by Denis Damiron, Jérôme Mazzolini, Fabrice Cousin, Christophe Boisson, Franck D’Agosto and Eric Drockenmuller Polym. Chem., 2012, 3, 1838-1845.

To keep up-to-date with all the latest research, sign up for the journal’s e-alerts or RSS feeds or follow Polymer Chemistryon Twitter or Facebook.

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Paper of the Week: From-syndiotactic-to-isotactic stereogradient polymers

Graphical abstract: From-syndiotactic-to-isotactic stereogradient methacrylic polymers by RAFT copolymerization of methacrylic acid and its bulky esters

Stereogradient polymers are a new class of polymers in which the tacticity continuously changes from one chain end to the other. Such polymers may exhibit special properties or functions that originate from gradual changes in the physical or chemical properties along the polymer backbone. In this article, the synthesis of stereogradient polymers with tacticities that vary from predominantly syndiotactic to highly isotactic was investigated by reversible addition–fragmentation chain transfer (RAFT) copolymerization of bulky methacrylates, such as triphenylmethyl methacrylate (TrMA) and 1-phenyldibezosuberyl methacrylate (PDBSMA) and methacrylic acid (MAA) in both non-polar and polar solvents. With the differing reactivities and stereospecificities or TrMA and MAA, the isotacticity of the resulting copolymer gradually increased from 11% to nearly 100% along the polymer chain. Interestingly, the reported method can be applied to the synthesis of various stereogradient poly(MAA)s or polymethacrylates by postpolymerization modification.

From-syndiotactic-to-isotactic stereogradient methacrylic polymers by RAFT copolymerization of methacrylic acid and its bulky esters by Kenji Ishitake , Kotaro Satoh , Masami Kamigaito and Yoshio Okamoto, Polym. Chem., 20123, 1750-1757.

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Conference: 2012 International Symposium on Stimuli-Responsive Materials, October 21-23

If you haven’t spotted it yet the 2012 International Symposium on Stimuli-Responsive Materials will be held 21st – 23rd October at the Hilton Sonoma Wine Country in Santa Rosa, CA.

Chaired by Marek Urban and Brent Sumerlin, the symposium will cover the design, synthesis, characterization, and understanding of the physical, chemical, and applied principles of stimuli-responsive materials and devices.

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Author of the Week: Gerard Lligadas

Dr Gerard Lligadas received his education in chemistry at the University Rovira i Virgili (URV), Tarragona, Spain. He continued his studies in Tarragona and completed his PhD in 2006 on exploring the utilization of plant oils as renewable feedstock in polymer chemistry. In 2007, a postdoctoral fellowship brought him to Penn University at Philadelphia, USA, where he worked under the direction of Prof. Virgil Percec on the elaboration of single-electron transfer living radical polymerization. At the end of 2008, he came back home becoming Lecturer and joining the Suspol Research Group at URV. His research interests include new bio-based polymers from renewable resources, halogen-free flame-retardant materials and controlled radical polymerization of acrylate and methacrylate monomers.

Research group’s website: http://www.quimica.urv.es/~w3qo/suspolymers/suspolymers

What was your inspiration in becoming a chemist? I had a really great chemistry teacher during high school. But I really got into the organic chemistry and polymer science world after listening to Prof. Juan C Ronda at the University. I got really fascinated by the way he feels science!

What was the motivation to write this article? (DOI: 10.1039/C2PY20273E) The key objectives of our research come under the broad heading of the sustainable polymer chemistry. In our searching of novel biobased polyols for polyurethane technology, we came a couple of years ago with the application of thiol-ene click chemistry to unsaturated fatty acid derivatives with hydroxyl-functionalized thiols. Here, our motivation was to make a step forward and apply thiol-yne coupling to alkyne-derivatized fatty esters for its ability to add double hydroxyl functionality without compromising ester functionality, which may be used for a further polyurethane modification.

Why did you choose Polymer Chemistry to publish your work? Polymer Chemistry attracted us because of the quality of the work it publishes. Moreover, it meets all the criteria of a modern journal: it has a wide scope, a broad readership and promises fast review process and publication – which I can now confirm from my own experience.

In which upcoming conferences may our readers meet you? In February, my wife and I welcomed our first kid. The rest of 2012 will be quite. Next year I plan to attend 3rd Frontiers in Polymer Science Symposium.

How do you spend your spare time? I try to get some quality time each day with my wife and I am also trying to keep active with triathlon…swimming, cycling and running is a perfect release of stress cocktail.

Which profession would you choose if you were not a scientist? Hard to say… but If I would not be a scientist, I would probably be a chef. I really enjoy trying out new recipes. My wife loves it!

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Paper of the Week: One pot synthesis of sugar sensors

Graphical abstract: Direct nitroxide mediated (co)polymerization of 4-vinylphenylboronic acid as route towards sugar sensors

The glucose blood level should be carefully monitored in people suffering from diabetes mellitus. In this view, a wide variety of glucose sensing molecules have been developed in the recent decades, based on boronic acid functionalized dyes that change colour or emission in the presence of glucose. The incorporation of boronic acid moieties as polymer side chains
indeed results in glucose responsive polymers that are insoluble in the absence of glucose and are solubilised in the presence of glucose due to the higher polarity of the stabilized tetragonal anionic boronic acid form. The present work of Hoogenboom and co-workers aims at developping a simple macromolecular synthesis procedure for the preparation of boronic acid containing polymers, making them accessible to a wide range of polymer scientists, beyond polymer chemists. They used a combination of commercial products; the unprotected 4-vinylphenylboronic acid (4-VBA) and the BlocBuilder alkoxyamine initiator for nitroxide mediated polymerization (NMP). The developed NMP method opens up new avenues towards 4-VBA containing polymers to evaluate glucose responsivity of various copolymers, including block copolymers for autonomous insulin delivery upon increasing glucose concentration.

Direct nitroxide mediated (co)polymerization of 4-vinylphenylboronic acid as route towards sugar sensors by Gertjan Vancoillie , Simon Pelz , Elisabeth Holder and Richard Hoogenboom, Polym. Chem., 20123, 1726-1729.

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