Functional aliphatic polycarbonates have attracted significant attention as materials for use as biomedical polymers in recent years. The incorporation of pendent functionality offers a facile method ...of modifying materials postpolymerization, thus enabling functionalities not compatible with ring‐opening polymerization (ROP) to be introduced into the polymer. In particular, polycarbonates bearing alkene‐terminated functional groups have generated considerable interest as a result of their ease of synthesis, and the wide range of materials that can be obtained by performing simple postpolymerization modifications on this functionality, for example, through radical thiol‐ene addition, Michael addition, and epoxidation reactions. This review presents an in‐depth appraisal of the methods used to modify alkene‐functional polycarbonates postpolymerization, and the diversity of practical applications for which these materials and their derivatives have been used.
The postpolymerization modification of alkene‐functional polycarbonates has been applied in recent years for the synthesis of a wide range of materials with diverse applications. Here, the broad range of uses for which alkene‐functional polycarbonates have been employed is reviewed, in order to demonstrate the scope of these materials for future applications in biomedicine and beyond.
The advent of additive manufacturing offered the potential to revolutionize clinical medicine, particularly with patient-specific implants across a range of tissue types. However, to date, there are ...very few examples of polymers being used for additive processes in clinical settings. The state of the art with regards to 3D printable polymeric materials being exploited to produce novel clinically relevant implants is discussed here. We focus on the recent advances in the development of implantable, polymeric medical devices and tissue scaffolds without diverging extensively into bioprinting. By introducing the major 3D printing techniques along with current advancements in biomaterials, we hope to provide insight into how these fields may continue to advance while simultaneously reviewing the ongoing work in the field.
The stereocomplexation of polylactide (PLA) has been widely relied upon to develop degradable, sustainable materials with increased strength and improved material properties in comparison to ...stereopure PLA. However, forming functionalized copolymers of PLA while retaining high crystallinity remains elusive. Herein, the controlled ring-opening copolymerization (ROCOP) of lactide (LA) and functionalized cyclic carbonate monomers is undertaken. The produced polymers are shown to remain crystalline up to 25 mol % carbonate content and are efficiently stereocomplexed with homopolymer PLA and copolymers of opposite chirality. Polymers with alkene and alkyne pendent handles are shown to undergo efficient derivatization with thiol–ene click chemistry, which would allow both the covalent conjugation of therapeutic moieties and tuning of material properties.
The crystallization-driven self-assembly of polymers based on semicrystalline poly(ε-caprolactone) cores is currently an area of high interest on account of their well-known biocompatibility and ...biodegradability, yet a comprehensive understanding of coil–crystalline–coil type triblock copolymer assembly behavior with respect to this core chemistry is yet to be realized. Herein, we demonstrate the simple preparation of well-defined tuneable 1D and 2D structures based on poly(ε-caprolactone) (PCL) triblock copolymers of different block ratios synthesized by ring-opening polymerization (ROP) and reversible addition–fragmentation chain transfer (RAFT) polymerization. In this report, the assembly of PCL-based amphiphiles in various solvents was investigated to tune the morphology and size of the assemblies with well-defined 2D platelets and long cylinders produced when using long soluble coronal blocks or under good solvent conditions. By contrast, truncated short fibers were obtained for less soluble PCL-containing block copolymers or under poor solubility conditions for the core block as a consequence of the increasing amount of nuclei formed in the crystallization process. Furthermore, the length of PCL-based 1D nanostructures could be controlled by tuning self-assembly conditions where the micelles’ lengths varied from 93 to 1200 nm with narrow dispersities. This easy assembly methodology greatly simplifies the lengthy procedure required to prepare biodegradable 1D and 2D nanostructures from PCL with tuneable sizes, which demonstrate great potential as drug-delivery vehicles in the realm of biomedicine.
Well-defined allyl-functional poly(carbonate)s were synthesized via the organocatalytic ring-opening polymerization of 5-methyl-5-allyloxycarbonyl-1,3-dioxan-2-one using the dual ...1-(3,5-bis(trifluoromethyl)phenyl)-3-cyclohexylthiourea and (−)-sparteine catalyst system. The resulting allyl-functional poly(carbonate)s obtained showed low polydispersities and high end-group fidelity, with the versatility of the system being demonstrated by the synthesis of block copolymers and telechelic polymers. Further functionalization of homopolymers with degrees of polymerization of 11 and 100 were realized via the radical addition of thiols to the pendant allyl functional groups, resulting in a range of functional aliphatic poly(carbonate)s.
Polyorthoesters are generally considered to be highly biocompatible, surface-eroding materials. However, sensitive intermediates and poor mechanical performance have largely prevented their ...widespread application to date. Herein, a simple and versatile method to synthesize orthoester- and acetal-based polymers is presented. Using 2-methylene-1,3-dioxe-5-pene as a stable bifunctional monomer, sequential highly selective “click” reactions led initially to the formation of orthoesters (OE) in a Markovnikov alcohol addition or acetals via anti-Markovnikov thiol–ene addition. Subsequent photoinitiated thiol addition onto the remaining endocyclic and backbone alkene functionalities lead to thioether formation to produce a class of poly(orthoester-thioether)s or poly(acetal-thioether)s via a step-growth polymerization. While all obtained polymers were found to possess a weight-average molecular weight of above 10 kg·mol–1, the application of an OE monomer with additional double bond functionality led to a cross-linked polymer network which displayed surface-erosion behavior.
New methods to introduce and control polymer network crosslinking and improve mechanical properties of the resulting materials have been investigated extensively. Common methods to enhance the ...mechanical properties of elastomers include “vulcanization” by which polymer chains are covalently crosslinked. In this work, we outline a new method to crosslink well-defined, synthetic elastomers using “click” reactions. Specifically, 2-butyne-1,4-diyl dipropiolate which possesses both external and internal alkynes, was synthesized as a functional monomer and copolymerized with dithiols to yield a series of elastomeric materials possessing variations in cis stereochemistry. Notably, the glass-transition temperature and mechanical properties of the resulting copolymers can be tuned by changing the stoichiometry between 2-butyne-1,4-diyl dipropiolate and 1,3-propane diyl dipropiolate. The alkyne functionalities within the backbone allow for post-polymerization interchain crosslinking to form polymer networks using a ruthenium-catalyzed azide–alkyne cycloaddition. Hysteresis tests have shown that tensile modulus and recovery can be controlled by the density of the crosslinking within the network.
The creation of nanoparticles with controlled and uniform dimensions and spatially defined functionality is a key challenge. The recently developed living crystallization-driven self-assembly (CDSA) ...method has emerged as a promising route to one-dimensional (1D) and 2D core-shell micellar assemblies by seeded growth of polymeric and molecular amphiphiles. However, the general limitation of the epitaxial growth process to a single core-forming chemistry is an important obstacle to the creation of complex nanoparticles with segmented cores of spatially varied composition that can be subsequently exploited in selective transformations or responses to external stimuli. Here we report the successful use of a seeded growth approach that operates for a variety of different crystallizable polylactone homopolymer/block copolymer blend combinations to access 2D platelet micelles with compositionally distinct segmented cores. To illustrate the utility of controlling internal core chemistry, we demonstrate spatially selective hydrolytic degradation of the 2D platelets-a result that may be of interest for the design of complex stimuli-responsive particles for programmed-release and cargo-delivery applications.
Complex biological tissues are highly viscoelastic and dynamic. Efforts to repair or replace cartilage, tendon, muscle, and vasculature using materials that facilitate repair and regeneration have ...been ongoing for decades. However, materials that possess the mechanical, chemical, and resorption characteristics necessary to recapitulate these tissues have been difficult to mimic using synthetic resorbable biomaterials. Herein, we report a series of resorbable elastomer-like materials that are compositionally identical and possess varying ratios of cis:trans double bonds in the backbone. These features afford concomitant control over the mechanical and surface eroding degradation properties of these materials. We show the materials can be functionalized post-polymerization with bioactive species and enhance cell adhesion. Furthermore, an in vivo rat model demonstrates that degradation and resorption are dependent on succinate stoichiometry in the elastomers and the results show limited inflammation highlighting their potential for use in soft tissue regeneration and drug delivery.
The development of photopolymers that can be depolymerized and subsequently re-cured using the same light stimulus presents a significant technical challenge. A bio-sourced terpenoid structure, ...l-carvone, inspired the creation of a re-curable photopolymer in which the orthogonal reactivity of an irreversible thioether and a dynamic thiol-Michael bond enables both photopolymerization and thermally driven depolymerization of mechanically robust polymer networks. The di-alkene containing l-carvone was partially reacted with a multi-arm thiol to generate a non-crosslinked telechelic photopolymer. Upon further UV exposure, the photopolymer crosslinked into a mechanically robust network featuring reversible Michael bonds at junction points that could be activated to revert, or depolymerize, the network into a viscous telechelic photopolymer. The regenerated photopolymer displayed intrinsic re-curability over two recycles while maintaining the desirable thermomechanical properties of a conventional network: insolubility, resistance to stress relaxation, and structural integrity up to 170 °C. Our findings present an on-demand, re-curable photopolymer platform based on a sustainable feedstock.
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