Noncopolymerization Approach to Copolymers via Concurrent Transesterification and Ring-Opening Reactions

Inter- and intrachain transesterification, normally regarded as a detrimental side reaction for the synthesis of polyesters, is utilized herein to formulate a novel strategy for the modification of polyesters. Addition of an organic superbase into the mixture of hydroxyl-terminated poly(ε-caprolactone) and an epoxide, for example, propylene oxide or 1,2-butylene oxide, triggers concurrent nucleophilic ring-opening of the epoxide and transesterification reaction. The synergetic effect enables convenient and efficient transformation of the polyester into poly(ester-ether) random copolymers and thus advances the preparation of functional degradable polymeric materials taking advantage of the variety of commercial and laboratory-made polyesters and epoxides.

Poly(trimethylene carbonate)-based polymers engineered for biodegradable functional biomaterials

This review presents recent examples of applications and functionalization strategies of poly(trimethylene carbonate), its copolymers, and its derivatives to exploit the unique physicochemical properties of the aliphatic polycarbonate backbone.

Synthesis of Functional Polyester Based on Polylactic Acid and Its Effect on PC12 Cells after Coupling with Small Peptides

Polyesters containing functional groups are a suitable candidate matrix for cell culture in tissue engineering. Three types of semicrystalline copolymer poly(L-lactide-co-β-malic acid) [P(LA-co-BMD)] with pendent carboxyl groups were synthesized in this study. The functional monomer 3(S)-[(benzyloxycarbonyl)methyl]-1,4-dioxane-2,5-dione (BMD) was synthesized usingL-aspartic acid. The copolymer P(LA-co-BMD) was then synthesized through ring-opening copolymerization ofL-LA and BMD, with dodecanol as initiator and stannous octoate as catalyst. Copolymer structure was characterized by1H nuclear magnetic resonance (1H NMR), gel permeation chromatography (GPC), and differential scanning calorimetry (DSC) analyses. Results of1H NMR and GPC analyses showed that the copolymers were synthesized successfully. DSC curves showed that the crystal melting peak and enthalpy decreased with increased BMD. The crystallinity of the copolymer was destroyed by the presence of the functional monomer. After deprotection, carboxyl groups were coupled with the isoleucine-lysine-valine-alanine-valine peptide throughN-hydroxysuccinimide/dicyclohexylcarbodiimide method. The small peptide was beneficial to the axon growth of PC12 cells.

Core cross-linked micelles of polyphosphoester containing amphiphilic block copolymers as drug nanocarriers

Poly(ethylene oxide)-b-polyphosphoester bearing unsaturations are promising materials for drug delivery applications.

Dual responsive polymeric nanoparticles prepared by direct functionalization of polylactic acid-based polymers via graft-from ring opening metathesis polymerization

Polylactic acid (PLA) has found widespread use in plastics and in biomedical applications due to its biodegradability into natural benign products. However, PLA-based materials remain limited in usefulness due to difficulty of incorporating functional groups into the polymer backbone. In this paper, we report a strategy for PLA functionalization that establishes the preparation of highly derivatized materials in which ring opening metathesis polymerization (ROMP) is employed as a graft-from polymerization technique utilizing a norbornene-modified handle incorporated into the PLA backbone. As a demonstration of this new synthetic methodology, a PLA-derived nanoparticle bearing imidazole units protected with a photolabile group was prepared. The morphology of this material could be controllably altered in response to exposure of UV light or acidic pH as a stimulus. We anticipate that this graft-from approach to derivatization of PLA could find broad use in the development of modified, biodegradable PLA-based materials.

One-pot Synthesis of Functional Poly(amino ester sulfide)s and Utility in Delivering pDNA and siRNA

The development of efficacious carriers is an important long-standing challenge in gene therapy. In the past few decades, tremendous progress has been made toward non-viral vectors for gene delivery including cationic lipids and polymers. However, there continues to be a need for clinically translatable polymer-based delivery carriers because they offer tunable degradation profiles and functional groups, diverse structures/morphologies, and scalability in preparation. Herein, we developed a library of 144 degradable polymers with varying amine and hydrophobic content via a facile method that involves thiobutyrolactone aminolysis and consequent thiol-(meth)acrylate or acrylamide addition in one-pot. The polymer platform was evaluated for pDNA and siRNA delivery to HeLa cells in vitro. Hydrophobically modified 5S, 2E1, 6CY1, 5CY2, and 2M1 grafted HEMATL polymers are capable of delivering pDNA depending on the chemical composition and the size of the polyplexes. Hydrophobically modified 5S and 2B grafted HEMATL and 5S grafted ATL polymers exhibit capability for siRNA delivery that approaches the efficacy of commercially available transfection reagents. Due to tunable functionality and scalable preparation, this synthetic approach may have broad applicability in the design of delivery materials for gene therapy.

Functional Degradable Polymers by Radical Ring-Opening Copolymerization of MDO and Vinyl Bromobutanoate: Synthesis, Degradability and Post-Polymerization Modification

The synthesis of vinyl bromobutanoate (VBr), a new vinyl acetate monomer derivative obtained by the palladium-catalyzed vinyl exchange reaction between vinyl acetate (VAc) and 4-bromobutyric acid is reported. The homopolymerization of this new monomer using the RAFT/MADIX polymerization technique leads to the formation of novel well-defined and controlled polymers containing pendent bromine functional groups able to be modified via postpolymerization modification. Furthermore, the copolymerization of vinyl bromobutanoate with 2-methylene-1,3-dioxepane (MDO) was also performed to deliver a range of novel functional degradable copolymers, poly(MDO-co-VBr). The copolymer composition was shown to be able to be tuned to vary the amount of ester repeat units in the polymer backbone, and hence determine the degradability, while maintaining a control of the final copolymers' molar masses. The addition of functionalities via simple postpolymerization modifications such as azidation and the 1,3-dipolar cycloaddition of a PEG alkyne to an azide is also reported and proven by (1)H NMR spectroscopy, FTIR spectroscopy, and SEC analyses. These studies enable the formation of a novel class of hydrophilic functional degradable copolymers using versatile radical polymerization methods.

Synthesis and click chemistry of a new class of biodegradable polylactide towards tunable thermo-responsive biomaterials

A new class of clickable and biodegradable polylactide was designed and prepared via bulk polymerization of 3,6-dipropargyloxymethyl-1,4-dioxane-2,5-dione (1) which was synthesized from easily accessible propargyloxylactic acid (5). A homopolymer of 1 and random copolymer of 1 with l-lactide were obtained as amorphous materials and exhibit low Tg of 8.5 and 34 °C, respectively, indicating their promising potentials for biomedical applications. The statistical nature of random copolymers was investigated by DSC analysis and 13C NMR spectroscopy, which implies the random distribution of terminal alkyne groups along the back bone of copolymers. The efficient click post-modification of this new class of polylactide with alkyl and mPEG azides affords novel hydrophilic biomaterials, which exhibit reversible thermo-responsive properties as evidenced by their tunable LCST ranging from 22 to 69 °C depending on the balance of the incorporated hydrophilic/hydrophobic side chains. These results indicate the generality of this new class of clickable polylactide in preparing novel smart biomaterials in a simple and efficient manner via click chemistry.

A degradable brush polymer–drug conjugate for pH-responsive release of doxorubicin

We report the synthesis, characterization andin vitroassessment of a degradable brush polymer–drug conjugate which can enable acid-triggered release of doxorubicin (DOX).

Synthesis of a library of propargylated and PEGylated α-hydroxy acids toward "clickable" polylactides via hydrolysis of cyanohydrin derivatives

A new simple and practical protocol for scalable synthesis of a novel library of propargylated and PEGylated α-hydroxy acids toward the preparation of "clickable" polylactides was described. The overall synthesis starting from readily available propargyl alcohol, bromoacetaldehyde diethyl acetal, and OEGs or PEGs was developed as a convenient procedure with low cost and no need of column chromatographic purification. The terminal alkyne functionality survives from hydrolysis of the corresponding easily accessible cyanohydrin derivatives in methanolic sulfuric acid. Facile desymmetrization, monofunctionalization, and efficient chain-elongation coupling of OEGs further enable the incorporation of OEGs to α-hydroxy acids in a simple and efficient manner. At the end, synthesis of allyloxy lactic acid indicates that an alkene group is also compatible with the developed method.