Archive for January, 2017

Paper of the month: Probing the causes of thermal hysteresis using tunable Nagg micelles with linear and brush-like thermoresponsive coronas

Blackman et al. report the synthesis of thermoresponsive polymers with tunable aggregation numbers in order to study the causes of thermal hysteresis.


Thermoresponsive polymers are materials that exhibit a change in their solubility over a temperature range. Thanks to this unique characteristic, these polymers can be used as smart and switchable materials for a wide range of biomedical applications. However, the cloud points upon cooling and heating a thermoresponsive polymer do not coincide because the process of equilibration takes time. The temperature interval between the cloud points upon cooling and heating is called hysteresis and the reversibility of these polymer’s thermal transitions can be influenced by many factors. In order to shine a light to these factors, O’Reilly, Gibson and Blackman synthesized well-defined, responsive amphiphilic block copolymers containing four different thermoresponsive corona blocks and assembled them in micellar structures in aqueous media. All micelles were designed to have tunable aggregation number enabling the study of the effects of altering the corona chemistry, chain confinement and core hydrophobicity on the thermoresponsive behavior, specifically the degree of hysteresis. It was found that higher core hydrophobicities were associated with a higher degree of hysteresis due to differences in core hydration. Linear corona chains capable of forming polymer-polymer hydrogen bonding interactions (e.g. pNIPAM) showed a greater hysteresis than those that could not (pDEAm). Importantly, the authors demonstrates that polymers with a brush-like architecture (pDEGMA and pOEGMA) exhibit irreversible phase transitions at a critical chain density, owing to irreversible nanoscale rearrangement in the precipitated bulk. These findings offer a deeper and more comprehensive understanding of stimuli-responsive self-assemblies and further highlight the complexity of hysteresis in thermoresponsive polymer systems.


Tips/comments directly from the authors:

1. It is important to use a Peltier system fitted with a reference cell with an internal temperature probe in order to accurately measure the hysteresis in the cooling curve. We have found that those without this feature typically over-estimate the hysteresis by a few degrees.
2. When synthesizing the pOEGMA-containing diblock copolymers, careful consideration of the RAFT CTA was necessary; the use of 2-Cyano-2-propyl dodecyl trithiocarbonate, as was employed for pDEGMA-containing diblock copolymers, resulted in a significant amount of high molecular weight polymers in the molecular weight distribution. Additionally, lower conversions had to be employed in order to reduce the presence of such species.
3. It was also important to employ multiple angle light scattering coupled with an algorithm such as REPES, which could enable us to investigate the molecular weights of the major fast mode and filter out scattering from spurious slow modes typically found in thermoresponsive polymer systems attributed to non-Brownian interactive behavior.


Read this paper for free until March 14th

Probing the causes of thermal hysteresis using tunable Nagg micelles with linear and brush-like thermoresponsive coronas
Polym. Chem., 2017, 8, 233-244.
DOI: 10.1039/C6PY01191H

About the Webwriter:Athina Anastasaki

Dr. Athina Anastasaki is a Web Writer for Polymer Chemistry. She is currently a Global Marie Curie Fellow working alongside Professor Craig Hawker at the University of California, Santa Barbara (UCSB). Please, visit her website for more information.

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Advisory Board Top Picks: Sophie Guillaume

Sophie Guillaume is a member of the Advisory Board for Polymer Chemistry and a CNRS Research Director at the Institut des Sciences Chimiques de Rennes (ISCR), France.

Her research focuses on the development of green pathways for the synthesis and structure–property relationships of synthetic polymers (especially polyesters, polycarbonates, polyolefins, and polyurethanes). Areas of emphasis include biobased degradable polymers and functionalized and reactive (co)polymers for advanced industrial and biomedical applications.

You can find all Advisory Board’s Top Picks papers in our web collection.

Focus on polyurethanes

All articles are free to read until Sunday 5th March.

Polyurethanes (PUs) are one of the most important classes of polymeric materials most widely used as coatings, adhesives, sealants, foams, or elastomers. These multiblock copolymers are formed by the stepwise addition of diols (or polyols) with diisocyanates (or polyisocyanates). Efforts to reduce their environmental impact and to improve their sustainability, resulted in the development of biobased monomers, and of greener processes towards non-isocyanate polyurethanes (NIPUs). Original PU materials with properties at least matching or improving those of the current PU market are thus being sought. To this end, functionalization introduced via the amine segment, the polyol moiety, or the repeating units’ pending groups, is a key parameter to tune towards the desirable characteristics and targeted applications. The biomedical field provides further opportunities for biocompatible and biodegradable PU materials which are widely used as nerve tissue scaffolds, vascular prostheses or drug delivery systems. However, their physical properties (mechanical properties, degradation performances and blood compatibility) still require improvements. These present trends are illustrated with the following top-picks.

Room temperature synthesis of non-isocyanate polyurethanes (NIPUs) using highly reactive N-substituted 8-membered cyclic carbonates

Alexander Yuen, Amaury Bossion, Enrique Gómez-Bengoa, Fernando Ruipérez, Mehmet Isik, James L. Hedrick, David Mecerreyes, Yi Yan Yang and Haritz Sardon
Polym. Chem., 2016, 7, 2105-2111

Current efforts in the polyurethane (PU) community aim at developing green strategies exempt of the use of toxic and dangerous isocyanates. Nowadays, the most promising route towards such non-isocyanate polyurethanes (NIPUs) is the aminolysis of dicyclic carbonates. H. Sardon and co-workers at the University of the Basque Country (Spain), have synthesized, at room temperature without the need for any additional catalyst, high molar mass NIPUs (up to 47 kg.mol1) from a (bis) N-substituted eight-membered cyclic carbonate (N-8CC) derived from renewable resources using a variety of diamines. These experimental results highlight the unique reactivity of this N-8CC over the smaller five- and six-membered cyclic carbonates, as further supported by computational insights which revealed a kinetically and theoretically more favourable ring opening of the N-8CC by an amine system.

Synthesis and hydrolytic properties of water-soluble poly(carbonate–hydroxyurethane)s from trimethylolpropane

Hiroyuki Matsukizonoa and Takeshi Endo
Polym. Chem., 2016, 7, 958-969

Poly(hydroxyurethane)s (PHUs) derived from the polyaddition of six-membered ring cyclic carbonates with diamines are promising non-isocyanate polyurethanes (NIPUs) alternatives to polyurethanes (PUs), as evidenced by T. Endo and co-worker at Kinki University (Japan). Such PHUs advantageously contain two primary hydroxyl groups in their side chains of repeating units, which improve the hydrophilicity and which can be chemically modified to design functional PHU materials. Original well-defined water-soluble poly(carbonate–hydroxyurethane)s comprising hydroxyurethane–carbonate–hydroxyurethane alternate structures were synthesized from trimethylolpropane and conventional diamines. Investigations of their hydrolytic properties in aqueous media at different pH values revealed their complete decomposition to their basic structures in carbonate buffers at pH 10.6 within one week.

Bio-based difuranic polyol monomers and their derived linear and cross-linked polyurethanes

Zehuai Mou, Shuo (Kelvin) Feng and Eugene Y. X. Chen
Polym. Chem., 2016, 7, 1593–1602

A series of linear and cross-linked polyurethanes (PUs) is reported by E. Chen and co-workers at Colorado State University (USA), from the catalysed polyadditions of diol, triol or tetraol derived from the biomass platform chemical 5-hydroxymethylfurfural (HMF) – one of the most value-added biomass building blocks or platform chemicals – with various diisocyanates in the presence of a catalyst (organocatalyst or dibutyltin dilaurate), respectively. The PU materials derived from the new diol monomer, namely 5,5’-bihydroxymethyl furil, and aromatic diisocyanates such as diphenylmethane diisocyanate, revealed valuable characteristics (Mn,SEC = ca. 40 kg mol−1, onset decomposition temperature = 234 °C, and Tg = 140 °C). Solvent casting from these PUs affords thin films ranging from brittle to flexible with a high strain at break of 300%.

An epoxy thiolactone on stage: four component reactions, synthesis of poly(thioether urethane)s and the respective hydrogels

Stefan Mommer, Khai-Nghi Truong, Helmut Keul and Martin Möller
Polym. Chem., 2016, 7, 2291–2298

The synthesis of a new epoxy thiolactone is described by H. Keul and M. Möller and co-workers at RWTH Aachen University (Germany), along with its ability to act in several concepts as a versatile tool towards polymeric materials. The reactivity of this epoxy thiolactone with an amine and catalytic amounts of a base, results in the selective ring opening of the thiolactone to generate an AB-type epoxy thiol monomer, which in situ starts a thiol-epoxy polymerization to ultimately form poly(thioether urethane)s (PTEUs). Besides the introduction of a new functionality – the organic residue – by the amine used for ring opening of the thiolactone, the PTEU backbone further exhibits a hydroxyl functionality. The latter increases the hydrophilicity of the polymer backbone and also provides a site for an additional functionalization. Two strategies were elaborated for the generation of functional gels from this epoxy thiolactone bis cyclic monomer, using a diamine or a triacrylate. These one pot processes are feasible and provide an interesting platform for a variety of polymer architectures hosting functionalities.

A novel biodegradable polyurethane based on poly(3-hydroxybutyrate-co-3-hydroxyvalerate) and poly(ethylene glycol) as promising biomaterials with the improvement of mechanical properties and hemocompatibility

Cai Wang, Yudong Zheng, Yi Sun, Jinsheng Fan, Qiujing Qina and Zhenjiang Zhao
Polym. Chem., 2016, 7, 6120-6132

A novel block polyurethane (PU) based on poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV), 4,4’-diphenylmethanediisocyanate and poly(ethylene glycol) (PEG) was synthesized by Zheng and co-workers at the University of Science and Technology Beijing (China), from the polyaddition of PHBV diol with ,-diisocyanate telechelic PEG. The resulting PU films exhibited biodegradability at 37 °C in phosphate buffer solution (PBS) at pH 7.4, non-cytotoxicity towards the growth and proliferation of the bone marrow mesenchymal stem cells, and hemocompatibility. The degradation rate results indicate that PHBV-based PUs are more suitable for biomedical applications requiring a longer degradation period. Greater PHBV contents also favourably influenced the mechanical properties and the thermal stability of these PU films. These new PHBV based PU materials with better mechanical properties, biodegradability, hemocompatibility and biocompatibility, may find potential applications in blood vessel tissue engineering.

Thermo- and pH-sensitive shape memory polyurethane containing carboxyl groups

Qiuju Song, Hongmei Chen, Shaobing Zhou, Keqing Zhao, Biqing Wang and Ping Hu
Polym. Chem., 2016, 7, 1739-1746

A multi-functional polyurethane (PU) with both a thermo-induced triple shape memory effect and a pH-sensitive dual shape memory effect has been developed by Chen and Hu and co-workers at Sichuan Normal University (China). The two-step polyaddition of polyethylene glycol (PEG), and 4,4’-diphenylmethane diisocyanate, followed by polymerization of the resulting diisocyanate end-functionalized PEG with dimethylolpropionic acid afforded the desired PUs bearing pendant carboxyl groups. In PU with 30wt% of PEG, the glass transition of PEG chains and the association/disassociation of carboxylic dimers act as two switches to control the triple-shape memory effect, while the carboxylic dimer is affected by pH values to associate in acidic solutions (pH 2) and dissociate in alkaline solutions (pH 9) to induce the pH-sensitive shape memory. The carboxylic dimers play an important role in the construction of shape memory properties in these PUs. Indeed, PUs with too high or too low carboxylic content (e.g. with 20 or 40wt% of PEG) did not exhibit any shape memory properties.

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Top 10 Most-accessed Polymer Chemistry articles – Q4 2016

This month sees the following articles in Polymer Chemistry that are in the top ten most accessed from October – December 2016:

Why not take a look at the articles today and blog your thoughts and comments below.

Lignocellulosic biomass: a sustainable platform for the production of bio-based chemicals and polymers
Furkan H. Isikgor and C. Remzi Becer
Polym. Chem., 2015,6, 4497-4559
DOI: 10.1039/C5PY00263J

Thiol-ene “click” reactions and recent applications in polymer and materials synthesis
Andrew B. Lowe
Polym. Chem., 2010,1, 17-36
DOI: 10.1039/B9PY00216B

Thiol–ene “click” reactions and recent applications in polymer and materials synthesis: a first update
Andrew B. Lowe   
Polym. Chem., 2014,5, 4820-4870 
DOI: 10.1039/C4PY00339J

The power of light in polymer science: photochemical processes to manipulate polymer formation, structure, and properties
Shunsuke Chatani, Christopher J. Kloxin and Christopher N. Bowman
Polym. Chem., 2014,5, 2187-2201
DOI: 10.1039/C3PY01334K

Facile and efficient chemical functionalization of aliphatic polyesters by cross metathesis
Lucie Fournier, Carine Robert, Sylvie Pourchet, Alice Gonzalez, Lewis Williams, Joëlle Prunet and Christophe M. Thomas
Polym. Chem., 2016,7, 3700-3704
DOI: 10.1039/C6PY00664G

An aggregation-induced emission star polymer with pH and metal ion responsive fluorescence
Yuming Zhao, Wen Zhu, Ying Wu, Lin Qu, Zhengping Liu and Ke Zhang
Polym. Chem., 2016,7, 6513-6520
DOI: 10.1039/C6PY01488G

Facile preparation of pH-responsive AIE-active POSS dendrimers for the detection of trivalent metal cations and acid gases
Yunfei Zuo, Xing Wang, Yanyu Yang, Da Huang, Fei Yang, Hong Shen and Decheng Wu
Polym. Chem., 2016,7, 6432-6436
DOI: 10.1039/C6PY01618A

Multiple stimuli-responsive supramolecular gels constructed from metal–organic cycles
Lijie Li, Yong Cong, Lipeng He, Yongyue Wang, Jun Wang, Fu-Ming Zhang and Weifeng Bu
Polym. Chem., 2016,7, 6288-6292
DOI: 10.1039/C6PY01580H

Pluronic® block-copolymers in medicine: from chemical and biological versatility to rationalisation and clinical advances
Anaïs Pitto-Barry and Nicolas P. E. Barry
Polym. Chem., 2014,5, 3291-3297
DOI: 10.1039/C4PY00039K

End group removal and modification of RAFT polymers
Helen Willcock and Rachel K. O’Reilly
Polym. Chem., 2010,1, 149-157
DOI: 10.1039/B9PY00340A

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Advanced Polymers via Macromolecular Engineering (APME 2017)

We are delighted to announce that the Advanced Polymers via Macromolecular Engineering (APME 2017) conference will be held in Ghent, Belgium on 21 – 25 May 2017.

21 – 25 May 2017, Ghent, Belgium

The 12th International Conference on “Advanced Polymers via Macromolecular Engineering” (APME 2017) will be hosted by the Centre of Macromolecular Chemistry (CMaC) at Ghent University, Belgium on 21 – 25 May 2017.

APME 2017 will continue the tradition of successful polymer meetings, after the previous conference held in Yokohama in 2015. The APME2017 meeting will focus on macromolecular engineering for the design of advanced polymeric structures, relating to their characterisation and recent applications. The meeting will be excellent platform for macromolecular engineers and scientists to present their research and exchange ideas through fruitful discussions, in the beautiful city of Ghent.

After the last plenary lecture on 24 May 2017, a football game is announced, opposing the “Belgian polymer team” and the “Rest of the World polymer team”.

The main topics will include:

  • Recent Advances in Macromolecular Synthesis
  • Complex Macromolecular Structures
  • Dynamic and Supramolecular Polymers
  • Stimuli-responsive and Functional Polymer Architectures
  • Self-healing and Reprocessable Polymer Systems
  • Polymers at Surfaces and Interfaces
  • New Industrial Developments for Polymeric Materials
  • Polymers meet Biology/Biochemistry
  • Polymers from Renewable Resources
  • Polymers for Energy Applications

Registration deadline is 15 Januray 2017 – only a few days left, don’t delay!

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