Archive for the ‘Paper of the Month’ Category

Paper of the month: Surface-attached poly(phosphoester)-hydrogels with benzophenone groups

The undesired adsorption of bacteria, proteins and other biomolecules on surfaces of biomedical devices often triggers the formation of biofilms causing severe systemic infections. In order to circumvent this, functional polymeric coatings with antifouling and/or antimicrobial properties are typically used. Towards this direction, Wurm, Lienkamp and co-workers developed photo-reactive poly(phosphoester)s (PPEs) which form surface-attached polymer networks and hydrogels. To achieve this, a benzophenone-functionalized cyclic phosphate monomer was synthesized and subsequently copolymerized with ethylene ethyl phosphate (EEP) yielding hydrophilic functional polymers. Upon terpolymerization with additional comonomers polymeric materials with pentyl (PEP), furfuryl (FEP) or butenyl (BuEP) pendants groups were obtained. Importantly, all polymerizations were well-controlled with good agreement between theoretical and experimental molecular weights and low dispersity values. The copolymerization kinetics were carefully monitored via real-time 31P nuclear magnetic resonance spectroscopy indicating a gradient-like structure. The cross-linked surface attached PPE networks were then formed by spin-coating these polymers onto pre-functionalized substrates followed by UV irradiation. Importantly, the layer thickness could be varied between 56 and 263 nm and was dependant on the applied polymer and the hydrophilicity of the substrates. Atomic force microscopy was also employed to further characterize these materials showing a homogeneous and smooth morphology with static contact angles of 20-26° (for specific networks) and revealing hydrophilic surfaces. Given the biocompatible nature of PPEs, these networks can potentially be promising anti-fouling coatings candidates for biomedical devices such as implants or catheters. In addition, initial functionalization of the substrates using furane-containing PPE-coatings demonstrated that additional modifications can be performed therefore paving the way for more complex surface architectures.

Surface-attached poly(phosphoester)-hydrogels with benzophenone groups

Tips/comments directly from the authors:  

  1. Synthesis of PPEs must be conducted under strict exclusion of moisture.
  2. The resulting copolymers are extremely hydrophilic. Thus, care must be taken to immediately cross-link them after spin-coating, or else they will de-wet from the surface.

Surface-attached poly(phosphoester)-hydrogels with benzophenone groups, Polym. Chem., 2018, 9, 315-326, DOI: 10.1039/c7py01777d

 

About the webwriter
Athina
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 this site for more information.

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Paper of the month: The power of the ring: a pH-responsive hydrophobic epoxide monomer for superior micelle stability

Paper of the month DecemberPolymeric amphiphiles can find use in a wide range of applications including detergents, catalysts and drug delivery vehicles. However, new polymeric biocompatible micelles with increased stability, loading efficiency and degradability are still required to address related challenges in the drug delivery field. To this end, Kim and co-workers designed and synthesized a novel epoxide monomer namely tetrahydropyranyl glycidyl ether (TGE). A series of amphiphilic diblock co-polymers were subsequently synthesized with PTGE consisting of a hydrophobic pH-responsive block with poly ethylene glycol (PEG) being the hydrophilic part. These PEG-b-PTGE diblock copolymers showed superior stability in biological media, higher loading capacity, tunable release and controllable degradation when compared to the acrylic analogue 1-ethoxyethyl glycidyl ether (EEGE). The enhanced stability and tunability of the PTGE block were attributed to the increased hydrophophicity and the tight association between the chair conformations of the cyclic TGE side chains. All diblock copolymers exhibited low dispersity values and controlled molecular weights. The high stability of these micelles in combination with their high biocompatibility highlight their potential to be used in drug delivery. In summary, the developed new class of monomers and polymers will contribute to the advanced of polyethers as promising candidates for biomedical applications and beyond.

Tips/comments directly from the authors:  

  1. The synthesis of the TGE monomer is a very simple, one-step procedure, but the moisture should be strictly controlled during the synthesis. The residual water can result in byproduct, thus lowering the yield after purification.

  2. The polymerization using organic superbase t-BuP4 is a very simple and reliable method; however, the t-BuP4 must be handled and stored carefully by removing the moisture. Otherwise, it may cause a lower degree of polymerization than targeted one and self-initiation process. Thus, any source for moisture should be carefully removed in solvent, initiator and monomer.

The power of the ring: a pH-responsive hydrophobic epoxide monomer for superior micelle stability, Polym. Chem., 2017, 8, 7119-7132, DOI: 10.1039/c7py01613a

About the webwriter
Athina

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 this site for more information.

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Paper of the month: Dual stimuli responsive self-healing and malleable materials based on dynamic thiol-Michael chemistry

Dynamically crosslinked polymeric materials have received significant attention owing to their unique characteristics including the introduction of mechanical properties and the possibility to extend a material’s lifetime. These materials can typically find use in a wide range of applications such as coatings and elastomers. Konkolewicz and co-workers significantly contributed towards this direction by developing a facile synthesis of dynamic materials with thiol-maleimide based adducts. Maleimides are of particular importance as they consist of a highly reactive vinyl group for thiol-Michael addition reactions and typically demonstrate very high yields under mild conditions. To synthesize such materials, a thiol-maleimide cross linker (2-((1-(2-(acryloyloxy)ethyl)-2,5-dioxopyrrolidin-3-yl)thio)ethylacrylate) was initially synthesized and subsequently incorporated into a polymer matrix of hydroxyethyl acrylate. The properties of the elastomeric materials were then carefully evaluated by tensile testing, creep recovery, swelling studies, differential scanning calorimetry and rheological experiments. It was found that these polymeric materials showed dynamic behaviours like self-healing and malleability at elevated pH values and temperatures. In addition, these materials possess significant healing properties and are mechanically stable towards creep deformation at room temperature and pressure. Their stimuli responsive self-healing, elastic, malleable and mechanically stable nature in combination with the facile nature of the synthesis paves the way for potential utilization in different applications that require enhanced properties and functions.

Dual stimuli responsive self-healing and malleable materials based on dynamic thiol-Michael chemistry

Tips/comments directly from the authors:

1. The synthetic techniques used to make the thiol-Michael based crosslinker (TMMDA) are very simple, but extra care should be given to store the crosslinker in the refrigerator or freezer. Storing the crosslinker at room temperature may result in background polymerization and eventually lead to loss of the crosslinker.

2. Although conventional free radical polymerization was used as a tool for polymerization, other polymerization techniques can be used as well. Although, reactivity of the thiol moiety has to be considered in that case.

3. Self-healing polymers are commonly responsive to single stimulus (e.g. temperature responsive Diels-Alder based polymer or light responsive disulfide polymer). TMMDA crosslinked materials developed in this paper have self-healing properties with both temperature and pH stimulus, giving them enhanced functionality and responsive character.

4. Dynamic materials synthesized in this article, based on the thiol-Michael reaction, showed malleability or reshape ability in response to both elevated temperature and pH. As a result, materials can be re-shaped into new configurations upon application of stimuli.

5. The thiol-Michael adducts are essentially static in the absence of thermal and pH stimulus, making the materials mechanically stable and creep resistant under ambient conditions.

 

Dual stimuli responsive self-healing and malleable materials based on dynamic thiol-Michael chemistry, Polym. Chem., 2017, 8, 6534-6543, DOI: 10.1039/C7PY01356F

 

About the webwriter

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 this link for more information.
Athina

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Paper of the month: Polymer synthesis by mimicking nature’s strategy: the combination of ultra-fast RAFT and the Biginelli reaction

Nature is capable of synthesizing an unlimited number of biomacromolecules (e.g. proteins) with remarkable structures and functions by simply starting from only 20 amino acids. This process lies in the precise sequence-controlled polymerization of amino acids to control the primary structures of polypeptide precursors, followed by a highly efficient post-translation modification in order to define these structures.

Polymer synthesis by mimicking nature’s strategy

Inspired by nature’s strategy to synthesize proteins, Tao and co-workers developed a two-stage method to synthesize a large number of polymers with precisely controlled structures, different functionalities and various molecular diversities. Key to their strategy is the combination of controlled radical polymerization and post-polymerization modification. Specifically, reversible addition-fragmentation chain transfer (RAFT) polymerization was utilized to synthesize the polymer precursors starting from only 3 acrylamide monomers. By repeating the polymerization with different monomer sequences, 6 triblock copolymers with controlled chain ends, molecular weights and molar mass distributions were obtained. The different polarity of all synthesized precursors was then confirmed by reverse-phase high performance liquid chromatography (HPLC). The triblock copolymers were subsequently modified via the Biginelli reaction to rapidly generate 60 derivatives in a high-throughput (HPT) manner. HTP analyses was also conducted as an efficient and quick way to verify specific functionalities (e.g. radical scavengers, metal chelating agents, etc.).

In summary, the authors presented an efficient strategy to prepare and characterize large libraries of polymers with diverse structures and functions.

Tips/comments directly from the authors:

1. For the Biginelli reaction, acetic acid/MgCl2 is an efficient solvent/catalyst system to smoothly get the targeted compounds. However, this system is not as efficient for aliphatic aldehydes. Fortunately, the Biginelli reaction has been studied for more than 100 years and as such, many other solvent/catalyst systems have been established in this time. Thus, people can choose different conditions to perform the Biginelli reaction for the post-polymerization modification depending on the specific requirements and applications.

2. For the high throughput analysis of radical scavengers, the oxygen in the air might also quench the radical, and the radical colour was found to fade faster in summer than in winter. Thus, the use of fresh reagents and careful recording of the temperature is recommended.

3. The ultra-fast RAFT was used in the present work as a model polymerization to prepare copolymers. The authors believe other advanced controlled radical polymerization techniques (SET-ATRP, photo-induced CRPs, sulfur-free RAFT, etc.) can also be used to prepare multiblock copolymers, especially when thermo-sensitive monomers are used.

Polymer synthesis by mimicking nature’s strategy: the combination of ultra-fast RAFT and the Biginelli reaction, Polym. Chem., 2017, 8, 5679-5687, DOI: 10.1039/c7py01313b

 

About the webwriter
Athina

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 this link for more information.

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Paper of the month: Sequence-coded ATRP macroinitiators

The development of strategies that allow the translation of the precise monomer sequence control achieved in nature over macromolecular structure (e.g. DNA) to whole synthetic systems is an exciting field in current polymer science. In particular, the fabrication of sequence-defined polymers paves the way for a diverse range of applications. For example, these macromolecules can be used to store monomer-coded information. Lutz and his team has pioneered this field and recently described the synthesis of digitally-encoded polyurethanes using an orthogonal solid-phase iterative approach. This class of materials is particularly interesting thanks to their unique physicochemical properties and straightforward sequencing by tandem mass spectrometry.

Sequence-coded ATRP macroinitiators

In the current contribution, Lutz and co-workers expand the application pool of these materials by covalently linking sequence-coded oligomers to other synthetic polymers. Sequence-coded oligourethanes were initially synthesized by orthogonal solid phase iterative chemistry on a modified Wang resin. While still attached to the solid support, the ω-OH-termini of the oligourethanes were transformed into atom transfer radical polymerization (ATRP) initiators by esterification with α-bromoisobutyryl bromide. Then, the oligomers were detached from the solid support and their cleaved α -COOH-termini were esterified with ethanol yielding monodisperse ATRP macro initiators. Upon polymerization of styrene from these precise oligomers, well-defined blocky architectures were obtained containing sequence-coded oligourethane segments. The polymerization was well-controlled, yielding materials with narrow molecular mass distributions and good agreement between theoretical and experimental molecular weights. Importantly, for a given macroinitiator length, the coded sequence of oligourethane had no influence on the ATRP process. Overall, these exciting results open up interesting perspectives for the development of plastic materials containing sequence-coded traceability barcodes.

Tips/comments directly from the authors:

  1. Sequence-coded oligourethanes have an interesting tendency to crystallize, which is currently under investigation. Consequently, these oligomers are usually relatively easy to characterize in solution directly after their synthesis but may become less soluble in standard solvents with time and storage.
  2. As mentioned in the communication, the tendency toward self-organization of the oligourethanes might influence their macroinitiator behavior. The preliminary results shown in this communication indicate that a controlled radical polymerization behavior is attainable with these macroinitiators. However, a deeper understanding of the initiation step is probably mandatory.
  3. The atom transfer radical polymerization of styrene was chosen as a simple polymerization model in the present work. Nevertheless, other controlled radical polymerization techniques might, of course, be considered for preparing such materials.

Sequence-coded ATRP macroinitiators Polym. Chem., 2017, 8, 4988-4991, DOI: 10.1039/C7PY00496F

 

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 this link for more information.

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Paper of the month: Block co-polyMOFs: assembly of polymer-polyMOF hybrids via iterative exponential growth and “click” chemistry

Block copolymer (BCP) assemblies are derived from covalently linked polymer chains and can undergo phase separation and thus find use in a wide range of applications including micropatterning, battery and electronic technologies. Metal-organic frameworks (MOFs) are another class of self-assembled matter consisting of crystalline networks with angstrom-scale order and permanent porosity. Owing to these advantageous properties, they can enable functions such as gas, energy storage, catalysis and selective-separation.

 

In the Johnson group, impressive efforts have been made to merge amorphous polymer networks with multi-component supramolecular assembly to generate soft materials with novel properties. In their current contribution, the group expands these types of hybrid materials by reporting a novel BCP where one block is a uniform benzene dicarboxylate (BDC)-based oligomer synthesized by iterative exponential growth (IEG), and the other is polystyrene (PS) prepared by atom transfer radical polymerization (ATRP). In order to achieve this, the authors initially synthesized the BDC-based oligomer with a defined end-functionality bearing an alkyne group that would allow for further diversification. This alkyne group was subsequently used to couple to azide-terminated polystyrene. In the presence of Zn ions, this BCP forms a “block co-polyMOF” (BCPMOF) material comprised of polyMOF domains embedded in a PS matrix.

The presented work is the first demonstration that it is possible to generate a crystalline polyMOF-amorphous polymer hybrid material from a single diblock copolymer. As such, BCPMOFs represent a new composite material that possesses the processability of the polymers while exhibiting enhanced stability towards ambient conditions when compared to the isolated MOFs. The ultimate goal of the group is to obtain BCPMOFs with robust mechanical properties, high surface areas, and tunable, well-defined domain sizes.

 

Tips/comments directly from the authors:

  1. In the synthesis of the mono benzylated diethyl 2,5-dihydroxyterephthalate, A, UV absorbance can readily distinguish the starting material from the product. The starting material elutes before the product and can be isolated for reuse.
  2. As noted in the supporting information, side products can occur during the coupling reaction to form L1. It is critical that ethanol is used to maintain the ethyl ester.
  3. The coupling reactions tend to require longer reaction times as the molecular weight of the reactants grows. Upon scaling up of the reactions, do not be temped to increase the concentration too much as it can lead to side product formation.
  4. The same synthetic protocols were used to form polyMOFs and block co-polyMOFs: 2.5 eq Zn(II) per BDC unit in Ln, was combined with Ln(PS) in DMF, heated at 100°C for 24h, followed by DMF washings to remove excess Zn(II) and unreacted ligand. Unlike the purification and isolation of L2 and L4, special care was taken for L4PS-Zn to use minimal organic solvent due to the solubility imparted by polystyrene.

 

Block co-polyMOFs: assembly of polymer-polyMOF hybrids via iterative exponential growth and “click” chemistry
Polym. Chem., 2017, 8, 4488-4493, DOI: 10.1039/c7py00922d

 

About the web writer


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 this website for more information.

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Paper of the month: Acceleration and improved control of aqueous RAFT/MADIX polymerization of vinylphosphonic acid in the presence of alkali hydroxides

Phosphonic acid functionalized polymers find use in a wide range of applications such as metal protection, polymer electrolyte membranes flame retardancy and dentistry. This is thanks to their unique characteristics including their acidic nature, stability, proton conductivity and metal binding ability. Vinyl phosphonic acid (VPA) in particular is a structurally simple example of such monomers which is not only affordable but also provides with a polymer (PVPA) with phosphonic acid groups that are directly attached to the backbone.

 

 

Despite the popularity and applicability of this polymer, the polymerization of VPA is typically slow yielding incomplete conversions which necessitates the need for additional costly and time-consuming purification steps. Destarac, Harrisson and co-workers were capable to circumvent this by investigating the effect of adding various alkali hydroxides to the conventional (free radical) and reversible addition-fragmentation transfer polymerization/macromolecular design by interchange of xanthates (RAFT/MADIX) radical polymerizations. Both types of polymerizations were strongly affected by the addition of NaOH. The authors found that by adding 1 equivalent of NaOH they could significantly increase the rate of the polymerization and the final conversion for both conventional and RAFT/MADIX polymerizations while larger quantities led to retardation of the reaction. A wide range of alkali hydroxides were also studied including H+, Li+, K+ and NH4+. It was shown that the dispersity of the final polymer decreases as the ionic radius of the counterion increases (H+ > Li+> Na+ > K+ > NH4+) while the acceleration of the polymerization follows the order Na+ > K+ > NH4+> Li+ > H+). Overall, the fastest rates of polymerizations were obtained in the presence of 0.5 equivalent of NaOH, while the same concentration of KOH or NH4OH allowed for a moderate acceleration on the polymerization rate combined with an improved control over the molar masses. Thus, this simple and cost-effective strategy can significantly improve the efficiency of the polymerization of VPA by simultaneously enhancing the reaction rate and the control over the molar masses.

 

 

Tips/comments directly from the authors:

  1. Take care to control the temperature when neutralizing the VPA – the reaction is very exothermic!
  2. Use NaOH for the most significant acceleration of polymerization and NH4OH for the strongest reduction in dispersity of the polymer.
  3. PVPA homopolymer can be precipitated in MeOH, but many PVPA-containing DHBCs must be purified by dialysis due to the small difference in solubility between PVPA and VPA and the low volatility of VPA.

 

Read this exciting research for free until 10/09/2017 through a registered RSC account.

Acceleration and improved control of aqueous RAFT/MADIX polymerization of vinylphosphonic acid in the presence of alkali hydroxides
Polym. Chem., 2017, 8, 3825-3832, DOI: 10.1039/c7py00747g

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About the webwriterAthina 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 this website for more

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Paper of the month: Structure/property relationships in copolymers comprising renewable isosorbide, glucarodilactone, and 2,5-bis(hydroxymethyl)furan subunits

Polyesters obtained from bio-derived monomers are often used as building blocks with the ultimate aim of meeting consumer demands for high-performance and sustainable materials. To this end, Reineke, Tolman, and Lillie sought to establish how changing the ratio of the sustainable D-glucaro-1,4:6,3-dilactone containing α, ω-diene (GDLU) and isosorbide undecanoate (IU) may influence the thermal, chemical and mechanical properties of the acyclic diene metathesis (ADMET)-derived polymers. The authors synthesized a series of random copolymers consisting of a range of GDLU and IU compositions and fully characterized them by uniaxial tensile testing, small-amplitude oscillatory shear rheology, X-ray scattering, and hydrolytic degradation testing.

 

It was found that small compositional changes have a detrimental impact on their mechanical performance and degradability. In addition, the authors investigated which carbohydrate-based building block was most important in promoting the elasticity and shape-memory abilities of this class of materials. To address this issue, GDL or isosorbide were replaced with a different sustainable diol, 2,5-bis(hydroxymethyl) furan. Studies of the resulting copolymers indicated that GDLU is responsible for imparting both elasticity and shape memory properties. Further, more economical and environmentally-friendly routes for the synthesis of GDLU and IU feedstocks were also explored.

 

Tips/comments directly from the authors:

  1. Acetonitrile appears to be the essential solvent for the scandium triflate-catalyzed esterification of GDL with 10-undecenoic acid anhydride.
  2. 10-Undecenoic acid anhydride can rapidly degrade on wet silica gel. To prevent this, oven dry (120 °C) the silica gel prior to its use and minimize the excess 10-undecenoic acid anhydride used in the reaction.
  3. Due to the hydrolytic instability of GDL and GDL-containing polymers, they should be stored in a vacuum desiccator to protected from moisture to prevent degradation between uses.

 

Read this exciting research for free until 13/08/2017 through a registered RSC account.

 

Structure/property relationships in copolymers comprising renewable isosorbide, glucarodilactone, and 2,5-bis(hydroxymethyl)furan subunits
Polym. Chem., 2017, 8, 3746-3754, DOI: 10.1039/c7py00575j

 

 

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About the webwriterAthina 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 this website for more

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Paper of the month: Block copolymer synthesis in one shot: concurrent metal-free ATRP and ROP processes under sunlight

Block copolymers are of a great interest to the polymer chemistry community as they provide intermediate physicochemical properties when compared to the respective homopolymers. Sequential monomer addition, mechanistic transformation and coupling of different segments are three of the most popular approaches to obtain block copolymers. However, all these approaches suffer from several drawbacks such as being limited to monomers that can be polymerized only under the same polymerization mechanism or requiring extreme experimental precautions and elongated purification steps.



In order to address the latter challenge, Yagci, Yilmaz and co-workers developed the first metal free example of block copolymer formation in which they concurrently polymerize structurally different monomers from a junction point serving as two functional groups for each polymerization. Since atom transfer radical polymerization (ATRP) and ring opening polymerization (ROP) are not expected to interfere with each other and as such could be the ideal candidates for such a system. In order to test this hypothesis, a specifically designed initiator was synthesized possessing a tertiary bromine at one end (capable of initiating an ATRP reaction) and a hydroxyl functionality at the other end (capable for initiating a ROP reaction). Under carefully optimized conditions and in the presence of both the ATRP and ROP catalysts both methyl methacrylate (MMA) and ε- caprolactone could be simultaneously polymerized yielding a diblock copolymer with good agreement between theoretical and experimental value sand low dispersity values. Interestingly, the reaction took place on the roof of the chemistry department at Istanbul technical university utilizing natural sunlight as the light source. The applicability of this technique was further demonstrated by the simultaneous polymerization of different sets of monomers including n butyl acrylate- ε- caprolactone and methyl methacrylate-lactide combinations. As such, the successful combination of ATRP with ROP in the same reaction media allows for the facile one pot synthesis of block copolymers which can find use in further applications where excess of metals or inorganic residues would be undesirable.

Tips/comments directly from the authors:

1. All chemicals should be added into the reaction tube under nitrogen atmosphere in dark (perhaps by covering the outside of the tube with an aluminium foil) to avoid any premature light induced polymerization.
2. ROP polymerization can take place even in dark. Therefore, the ROP catalyst should be added last, and afterwards, the reaction tube should be exposed to sunlight as soon as possible. This way, one can provide the optimum conditions for the polymerizations to be realized simultaneously.
3. The method is best applicable in sunny days. Sunlight was deliberately selected as the most natural and simple way of light exposure. However, various other irradiation sources that emit in the wavelength regions matching with the absorption of appropriate sensitizers can also be used.

Read this exciting research for free until 17/07/2017 through a registered RSC account.

 

Block copolymer synthesis in one shot: concurrent metal-free ATRP and ROP processes under sunlight
Polym. Chem., 2017, 8, 2899-2903, DOI: 10.1039/c7py00069c

 

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About the webwriterAthina 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 this website for more

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Paper of the month: Mild and efficient synthesis of ω,ω-heterodifunctionalized polymers and polymer bioconjugates

 

The versatile and high yielding modification of polymer end groups is a critical tool for controlling materials properties. However, when multiple different functionalities are needed, pre-installation of two different functional groups at the polymer end groups is typically a tedious requirement. Sumerlin, Castellano and co-workers managed to circumvent this by developing a mild approach that enables the efficient synthesis of ω-ω-heterodifunctionalized polymers and polymer bioconjugates. Key to this strategy is the use of the recently introduced reagent benzotrifuranone (BTF) which allows the introduction of differentially “clickable” functional groups to monomethyl ether poly(ethylene glycol) amine (mPEG amine). In contrast to conventional polymer heterofunctionalization approaches that require high temperatures, significant excess of reagents and numerous synthetic steps, BTF serves as an ideal functionalization handle that operates at ambient temperature using near-stoichiometric amounts of reagents. Importantly, following functionalization of BTF with alkyne and alkene functional groups a fluorescent (coumarin) dye and biotin could be successfully conjugated to the end of mPEG-amine. These polymer bioconjugates were then able to bind avidin while showing an unexpected disruption of avidin tetramer formation. Overall, the compatibility of BTF with a broad scope of amine nucleophiles and thermally sensitive moieties (e.g. proteins) in combination with the highly efficient and mild nature of this reagent holds great promise for more elaborate heterofunctionalization strategies.

 

 

Tips/comments directly from the authors:

 

  1. The reaction time of the first and second addition to BTF should be monitored (typically by thin layer chromatography) to ensure minimal over/under functionalization occurs.
  2. The trisubstitution products are tolerant to many reaction conditions; however, when performing reactions that include radical intermediates, higher than usual reagent equivalents may be needed due to the radical scavenging nature of the phloroglucinol
  3. When one-pot homodifunctionalizations are performed, be sure to add enough nucleophile to consume both electrophilic sites on the polymer end group and the three electrophilic sites on any unreacted BTF.
  4. Regarding BTF synthesis: 1) Using fresh polyphosphoric acid and monitoring the reaction temperature is very important for the ring-closing in the last step of the synthesis, and 2) BTF and the mono- and difuranone derivatives are sensitive to silica gel, so avoid letting the compounds reside in a column too long during purification.

 

Read this exciting research for free until 21/06/2017 through a registered RSC account.

 

Mild and efficient synthesis of ω,ω-heterodifunctionalized polymers and polymer bioconjugates
Polym. Chem., 2017,8, 2457-2461, DOI: 10.1039/C7PY00225D

 

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About the webwriterAthina 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 this website for more

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