# Enhancement of Mechanical Properties of PCL/PLA/DMSO2 Composites for Bone Tissue Engineering
## 1 Introduction  
Bone tissue engineering has the potential to aid in the regeneration or substitution of injured bone tissues through the utilization of biomaterials [1; 2; 3]. Biomaterials are employed across diverse medical and biomedical contexts owing to their distinctive characteristics and harmonization with biological systems [4; 5]. Biomaterials must fulfill the requirement of biocompatibility, biodegradability, strength, and durability to be used as structural support in medical implants, which did not cause side effects or rejection by the body [6; 7; 8; 9; 10; 11; 12]. Biomaterials can be gradually resorbed by the body, thus eliminating the need for surgical removal after the tissue regeneration process is complete [13; 14]. Polycaprolactone (PCL) and polylactic acid (PLA) are frequently reported as the most promising biocompatible and biodegradable polymers synthesized and were verified as biomaterials by the US Food and Drug Administration [15]. Dimethyl sulfone (DMSO2), well known as an organosulfur compound [16], is a non-hazardous and stable material [15]. In addition, DMSO2 has high surface tension and precise geometric accuracy with low viscosity in additive manufacturing [17]. PCL and PLA have been widely utilized as biomaterials that have gained significant attention in recent years due to their broad range of applications, including biomedical uses [18; 19], packaging [20; 21; 22; 23], and 3D printing [24; 25]. PCL is a polyester synthesized by the polymerization of the \(\varepsilon\)-caprolactone monomer, while PLA is a polyester derived from natural sources. PCL and PLA have good biocompatibility, various applications, and easy processing. On the other hand, both PCL and PLA have a low rate of degradation and low melt viscosity, leading to poor flow, low adhesion, and poor dimensional stability. In addition, PLA is relatively brittle [17], and PCL has relatively low strength and stiffness compared to other polymers [17; 26]. Several studies have been conducted to investigate the properties of PLA (worked as a matrix) and PCL (worked as an additive) composites. Some studies showed that as PCL content was increased, the modulus and yield strength of PCL/PLA composites were decreased, and toughness was decreased as well [27; 28]. [PERSON] et al. [29] studied the rheological, thermal, mechanical, and viscoelastic properties of biodegradable PLA/PCL composites. The elongation, impact toughness, and loss factor decreased compared to pure PLA, while the strength and modulus decreased. SEM analysis showed that PCL was dispersed homogeneously in the PLA matrix. [PERSON] and [PERSON] [30] reported on the influence of PCL on the crystallization behavior of PLA and PCL in various PLA/PCL composites. PCL in the composites significantly impacted the crystallization of PLA. The analysis of successive self-nucleation and annealing regarding PCL crystallization in the composites revealed a notable influence of the presence and quantity of PLA in the composites on the size distribution of crystals in PCL's primary crystalline fraction. [PERSON] et al. [31] researched a micromechanical analysis and the fracture mechanics of various PLA/PCL (from 10 up to 40 wt%) composites. Up to 20 wt% of PCL, debonding occurred, and void growth along the tensile direction occurred. When 40 wt% of PCL was applied, a significant enhancement in the elongation at break occurred due to the predominant shear strength. [PERSON] and [PERSON] [32] studied thermal behavior and mechanical properties. PLA/10 wt% PCL composites exhibited an optimum interfacial adhesion with an elongation at a break of 500.94% and a notched impact strength of 64.31 kJ/m\({}^{2}\). However, PCL/PLA composites have a limitation for the low rate of degradation. In order to solve this challenge, dimethyl sulfone (DMSO\({}_{2}\)) has emerged as an additive to control degradation time. Dimethyl sulfone (DMSO\({}_{2}\)) is a naturally occurring organosulfur compound known for its non-hazardous and stable properties [15; 33].