Nucleating and retarding effects of nanohydroxyapatite on the crystallization of poly(butylene terephthalate-co-alkylene dicarboxylate)s with different lengths

Abstract

New biodegradable and biocompatible composites are continuously developed for biomedical applications (e.g. from drug delivery devices to tissue engineering scaffolds). Properties of such systems may depend on their morphology and structure, which are attained after their processing and therefore, the study of the crystallization kinetics has a particular relevance. The crystallization kinetics of hydroxyapatite-filled poly(butylene terephthalate-co-alkylene dicarboxylate)s has been studied under non-isothermal conditions, using a wide range of cooling rates and different kinetic models. Based on our results, nanohydroxyapatite (nHAp) particles were found to effectively act as additional nucleation sites for poly(butylene terephthalate-co-succinate) (PBST), giving rise to an increased crystallization rate with respect to pure PBST. However, the overall growth rate of HAp nanocomposites decreased compared to the corresponding homopolymers with longer aliphatic dicarboxylic acids (i.e. adipic and sebacic acid derivatives). In order to clarify this point, the activation energy for non-isothermal crystallization was evaluated using the Friedman method and significant differences were observed, suggesting a disturbing effect of nanoparticles on the motion of molecular chains that hindered their capability to reach the growing crystallization front. Isoconversional methods provided a good understanding of the kinetics of the crystallization process and significant information regarding the activation energy, relative crystallinity, and global and local Avrami exponents.

Synthesis, Characterization and Properties of Biodegradable Poly(Butylene Sebacate-Co-terephthalate)

“…The lowest glass transition temperature ( T g) was observed in PBSeT64. PBSe exhibited −29.8 °C of T g and all of PBSeT samples showed the T g under −20 °C, which were similar to previously reported T g of synthesized aliphatic–aromatic copolymers with sebacate [ 24 , 25 ]. The low T g means that the polymers are in rubber state with possible elastomeric properties at room condition.…”

“…However, the peaks of the PBSeT spectra were more complex due to the combinations of the 1,4-butanediol, dimethyl terephthalate and sebacic acid monomers. In particular, some of the peaks corresponding to 1,4-butanediol signal were split by the strong signals of neighboring groups, such as the carbonyl and terephthalate groups [ 23 , 24 , 25 ].…”

“…The biodegradable aliphatic polymer poly(butylene sebacate) (PBSe) can also be obtained through the polymerization of Se as a dicarboxylic acid with butanediol [ 24 ]. Furthermore, to control the physicochemical properties of Se-based polymers, biodegradable poly-aliphatic/aromatic materials can also be prepared by adding a monomer with an aromatic group [ 23 , 24 , 25 ]. Poly(butylene sebacate- co -terephthalate) (PBSeT) with about 19,000 g/mol of molecular weight has been synthesized using different compositions of Se and terephthalic acid and the most amorphous PBSeT (5:5 sebacic acid/ terephthalic acid mole ratio) sample showed highly promising biodegradable characteristics [ 24 ].…”

Nano-hydroxyapatite-assisted enzyme-induced carbonate precipitation enhances Pb-contaminated aqueous solution and loess remediation

“…By contrast, nucleated, chubby rod-shaped minerals were precipitated under EICP-nHAP. Compared to the non-nucleated minerals, the nucleated minerals featured higher stability since nHAP addressed the inability to provide nucleation sites by the urease ( Heidarzadeh et al, 2019 ). This also explained that the nucleated minerals were not precipitated arbitrarily but directionally.…”

The Relationship between Microstructure and Mechanical Properties of PBST Two-Component Crystalline Random Copolymers with Different BT Contents

“…The heating curves of the PBST copolymers ( Figure 2 b) with increasing the BT content showed an increased melting temperature and a sharp melting peak, suggesting the formation of perfect crystals. This was attributed to the increase in the chain length and the regularity of the PBT molecular chain in the PBST copolymer [ 21 , 42 , 43 ]. According to the formula X c = ∆H m /M PBT • ∆H m 0 , where ∆H m is the melt detail of PBT in the PBST copolymers, ∆H m 0 is the standard melt detail of pure PBT, ∆H m 0 = 144.5 J/g, and M PBT is the molar content of PBT in the copolymer, the crystallinity of the PBT chain segments in the PBST copolymer is shown in Table 3 .…”