Synthesis, structure, and physical properties of poly(trimethylene terephthalate)‐block‐poly(caprolactone) copolymers

Abstract

The series of poly(trimethylene terephthalate)-block-PCLT (PTT-block-PCLT) copolymers with different contents of PTT as rigid, and poly(caprolactone) (PCL) as flexible segments have been synthesized from dimethyl terephthalate (DMT), 1,3-bio-propanediol, and PCL diol) in a two-step process involving transesterification and polycondensation in the melt. The weight amount of flexible PCLT segments varied from 0 (homopolymer PTT), 25, 35 to 45%. The molecular structure of the synthesized copolymers was confirmed by nuclear magnetic resonance and Fourier transform infrared spectroscopy analyses. According to Hoy's method, one confirmed that PTT and PCL are likely miscible, as the difference of the solubility parameters of PTT and PCL block pairs, equals to 3.15 MPa 1/2 . Moreover, the phase structure and mutual miscibility for the series of PTTblock-PCLT copolymers was characterized by differential scanning calorimetry, dynamic mechanical thermal analysis, and wide-angle X-ray scattering measurements. In copolymers with 35 and 45 wt % of flexible segments, the crystalline phase is formed during annealing above glass-transition temperature of copolymer. These copolymers during cooling at the standard rate do not crystallize. It was also found that incorporation of PCLT flexible segments, due to the macrophase separated structure, cause the decrease of the melting point and glass-transition temperature, along with the tensile modulus and tensile strength of PTT-block-PCLT copolymers, and at the same time cause an increase in the value of the elongation at break. As a result of copolymerization of PTT with PCLT, one obtained multiblock copolymers with a heterophase structure. By changing the PTT/PCLT ratio, one obtained copolymers that differ in hardness and tensile strength.

Functional Properties of Poly(Trimethylene Terephthalate)-Block-Poly(Caprolactone) Based Nanocomposites Containing Graphene Oxide (GO) and Reduced Graphene Oxide (rGO)

“…Moreover, the PTT- block -PCL-T copolymer exhibited a cold crystallization peak at the temperature of 56 °C. A more detailed analysis of the whole series of block copolymers based on PTT (as rigid segment) and PCL-T (as flexible segment) was published in our previous work [33]. The use of GO and rGO did not cause significant changes in T g , but it slightly increased T m .…”

“…The polymer solution had a concentration of 0.5 g/dL. The measurement was carried on a capillary Ubbelohde viscometer (type Ic, K = 0.03294) following the procedure described in [33]. The measurements of the density of the dumbbell shape samples were carried out at 23 °C on hydrostatic scales (Radwag WPE 600C, Poland), calibrated according to standards with a known density.…”

“…The mechanical performance of the prepared materials was evaluated using Autograph AG-X plus (Shimadzu) tensile testing machine equipped with a 1 kN Shimadzu load cell, an optical extensometer, and the TRAPEZIUM X computer software, operated at a constant crosshead speed of 5 mm/min, following the procedure previously described in [33]. According to PN-EN ISO 527 standard, the tensile modulus, yield stress and strain, stress and elongation at break of the nanocomposites were determined.…”

“…% of PTT segments and 25 wt. % of PCL-T segments and nanocomposites were prepared by in situ polymerization in 1 dm 3 steel high-pressure reactor (Autoclave Engineers Pennsylvania, USA), following the procedure described in our previous work [33]. Graphene oxide (GO) and reduced graphene oxide (rGO) were dispersed in 400 mL of bio-PDO using ultra-high speed stirrer (Ultra-Turax T25, Wilmington, NC, USA) for 15 min and afterwards stirred by ultrasonicator (Homogenizer HD 2200, Sonoplus, Berlin, Germany) with the frequency of 20 kHz and power of 200 W. Subsequently, the dispersion was subjected to ultrasounds in the ultra-power lower sonic bath (BANDELIN, Sonorex Digitec, Berlin, Germany) with frequency of 30 kHz and power 140 W for 15 min.…”

“…Synthesis details and properties of a series of PTT- block -PCL-T were described in our previous work [33]. It was found that the most promising system for obtaining polymer nanocomposites containing graphene derivatives is the PTT- block -PCL-T 75/25 wt.%/wt.%.…”