A Biodegradable and Cross-Linkable Multiblock Copolymer Consisting of Poly(propylene fumarate) and Poly(ε-caprolactone):  Synthesis, Characterization, and Physical Properties

Abstract

In an effort to develop various controllable biomaterials, a series of novel cross-linkable and biodegradable multiblock poly(propylene fumarate-co-caprolactone) [P(PF-co-CL)] copolymers have been synthesized via a three-step polycondensation of oligomeric polypropylene fumarate (PPF) with polycaprolactone (PCL) diols. The chemical structures of 15 copolymers with various PCL compositions and segment lengths were further characterized by FTIR, 1 H NMR, and 13 C NMR spectra. Their physical and rheological properties have been determined extensively. The composition dependences of various characteristic temperatures such as glass transition temperature T g, melting temperature Tm, and thermal degradation temperature Td were demonstrated using a phase diagram. Together with DSC results, polarized optical microscopical graphs of several copolymers with high PCL compositions show spherulite crystalline structure. Particularly a banded spherulite has been found for a copolymer with a PCL composition of 87% when it crystallizes at room temperature. When the PCL composition in these copolymers is lower than 70%, the copolymers are amorphous with a reduced T g. This is critical for an enhanced rate of biodegradation. Because of the flexibility of PCL segments in the copolymers, P(PF-co-CL) can be either self-cross-linked or photocross-linked without using any cross-linker. The unentangled characteristics have been verified by the melt viscosity's molecular weight dependence and the master curves of storage modulus G′ and loss modulus G′′. The introduction of PCL into the copolymer chain enhances the solubility in toluene. Dilute solution viscometry shows the effect of microstructure in intrinsic viscosity while this effect is insignificant in melt viscosity. Therefore, the physical properties of such a copolymer can be modulated by the composition and segment length to satisfy the needs in a variety of tissue engineering applications such as bone, cartilage, and nerve tube regenerations.

Physical properties and cellular responses to crosslinkable poly(propylene fumarate)/hydroxyapatite nanocomposites

“…As described previously [31,32], diethyl fumarate (DEF) and excess amount of 1,2-propylene glycol were polymerized together with hydroquinone (crosslinking inhibitor) and zinc chloride (catalyst) first at 100 °C for 1 h and then 150 °C for 7 h to obtain the intermediate dimer. Then the intermediate dimer was transesterified to form PPF under vacuum at 130 °C for another 4 h. Gel permeation chromatography (GPC) was used to determine the molecular weight and polydispersity of PPF.…”

“…It is an unsaturated linear polyester that can be crosslinked through carbon-carbon double bonds along its backbone [26,27] and degraded through simple hydrolysis of the ester bonds into non-toxic products of propylene glycol, poly (acrylic acid-co-fumaric acid), and fumaric acid [28]. By controlling the molecular weight of PPF and the crosslinking density, the maximum compressive strength and modulus of crosslinked PPF can be over 10 and 100 MPa, respectively [29][30][31][32]. Although many previous studies have been performed to enhance both mechanical strength and osteoconductive properties by adding calcium phosphate such as β-tricalcium phosphate (β-TCP) to PPF [33,34], or preparing PPF/HA composites by either simple mixing [35] or from in situ precipitation [36], the correlation between the physical properties and cell responses on PPF/HA nanocomposites has not yet been reported, compared with other poly(α-hydroxyl acids)-based composites.…”

Fabrication and Characterization of Poly(Propylene Fumarate) Scaffolds with Controlled Pore Structures Using 3-Dimensional Printing and Injection Molding

“…PPF was synthesized as described previously. 27,28 Briefly, diethyl fumarate, excess amount of 1,2-propylene glycol were polymerized together with hydroquinone (crosslinking inhibitor) and zinc chloride (catalyst) first at 1008C for 1 h and then 1508C for 7 h to obtain fumaric diester intermediate. The intermediate was transesterified to form PPF under vacuum at 1508C for another 7 h. Gel permeation chromatography (GPC) was used to determine the molecular weights and polydispersity of PPF.…”

Synthesis, characterization and properties of amphiphilic block copolymers of 2-hydroxyethyl methacrylate and polydimethylsiloxane prepared by atom transfer radical polymerization

“…8 Varying the block characteristics allows for control over various polymer properties, such as crystallinity, glass transition, melting point and thermal degradation. 9 For example, the degree of swelling, optical transparency and mechanical properties of the block copolymers of poly(ethylene oxide) (PEO) and either poly(e-caprolactone) or poly(L-lactic acid) depend on the hydrophobic polymer block type and polymer composition. 10 Poly(2-hydroxyethyl methacrylate) is hydrophilic acrylic polymer with unique assets, including transparency, good mechanical properties and biocompatibility.…”