Polymer Chemistry Blog

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.

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

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.

Polymeric 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

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.