Polyurethane triblock copolymers with mono-disperse hard segments. Influence of the hard segment length on thermal and thermomechanical properties

2008 ◽  
Vol 48 (6) ◽  
pp. 1222-1230 ◽  
Author(s):  
Araichimani Arun ◽  
Kasper K.J. Baack ◽  
Reinoud J. Gaymans
Keyword(s):  
Hard Segment ◽  
Triblock Copolymers ◽  
Thermomechanical Properties ◽  
Segment Length ◽  
Hard Segments

scholarly journals Quadruple Hydrogen Bond-Containing A-AB-A Triblock Copolymers: Probing the Influence of Hydrogen Bonding in the Central Block

Molecules ◽  
2021 ◽  
Vol 26 (15) ◽  
pp. 4705
Author(s):  
Boer Liu ◽  
Xi Chen ◽  
Glenn A. Spiering ◽  
Robert B. Moore ◽  
Timothy E. Long
Keyword(s):  
Hydrogen Bonding ◽  
Self Assembly ◽  
Microphase Separation ◽  
Triblock Copolymers ◽  
Random Copolymer ◽  
Thermomechanical Properties ◽  
Structure Property ◽  
Scanning Calorimetry ◽  
Central Block ◽  
Quadruple Hydrogen Bonding

This work reveals the influence of pendant hydrogen bonding strength and distribution on self-assembly and the resulting thermomechanical properties of A-AB-A triblock copolymers. Reversible addition-fragmentation chain transfer polymerization afforded a library of A-AB-A acrylic triblock copolymers, wherein the A unit contained cytosine acrylate (CyA) or post-functionalized ureido cytosine acrylate (UCyA) and the B unit consisted of n-butyl acrylate (nBA). Differential scanning calorimetry revealed two glass transition temperatures, suggesting microphase-separation in the A-AB-A triblock copolymers. Thermomechanical and morphological analysis revealed the effects of hydrogen bonding distribution and strength on the self-assembly and microphase-separated morphology. Dynamic mechanical analysis showed multiple tan delta (δ) transitions that correlated to chain relaxation and hydrogen bonding dissociation, further confirming the microphase-separated structure. In addition, UCyA triblock copolymers possessed an extended modulus plateau versus temperature compared to the CyA analogs due to the stronger association of quadruple hydrogen bonding. CyA triblock copolymers exhibited a cylindrical microphase-separated morphology according to small-angle X-ray scattering. In contrast, UCyA triblock copolymers lacked long-range ordering due to hydrogen bonding induced phase mixing. The incorporation of UCyA into the soft central block resulted in improved tensile strength, extensibility, and toughness compared to the AB random copolymer and A-B-A triblock copolymer comparisons. This study provides insight into the structure-property relationships of A-AB-A supramolecular triblock copolymers that result from tunable association strengths.

Effect of chain segment length on crystallization behaviors of poly(l-lactide-b-ethylene glycol-b-l-lactide) triblock copolymer

2019 ◽  
Vol 28 (2) ◽  
pp. 77-88
Author(s):  
Yongji Gong ◽  
Weihua Song ◽  
Yifan Wu ◽  
Daohai Zhang ◽  
Yufei Liu ◽  
...  
Keyword(s):  
Growth Rate ◽  
Ethylene Glycol ◽  
Chain Length ◽  
Triblock Copolymer ◽  
Triblock Copolymers ◽  
Segment Length ◽  
Resonance Spectroscopy ◽  
Chain Segment ◽  
Scanning Calorimetry ◽  
Crystallization Behaviors

The poly(l-lactide-b-ethylene glycol-b-l-lactide) (PLLA-PEG-PLLA) triblock copolymers with different chain segment length are fabricated by ring-opening polymerization. The structure, molecular weight, and crystallization behaviors of the triblock copolymers are characterized by Fourier transform infrared, nuclear magnetic resonance spectroscopy, gel permeation in chromatography, X-ray diffraction, differential scanning calorimetry, and polarizing optical microscopy (POM). The results show that the increase of block length is beneficial to improve its crystallization. In addition, the triblock copolymer exhibits a double crystallization phenomenon. The POM results indicate that PEG and PLLA chains of the copolymer crystallize in their respective crystallization temperature regions. The growth rate of the PLLA spherocrystal decreases and the dendritic spherocrystals appear with increasing the PEG chain length when the PLLA chain of the copolymer is isothermal crystallized at 80°C and PLLA chain length is constant. The growth rate of the PEG spherocrystal decreases and the spherocrystal morphology changes little with increasing PLLA chain length when the PEG chain is isothermal crystallized at 25°C and the length of PEG chain remained unchanged.

Properties of polyether-polyurethane block copolymers: effects of hard segment length distribution

1985 ◽  
Vol 18 (1) ◽  
pp. 32-44 ◽  
Author(s):  
John A. Miller ◽  
Shaow B. Lin ◽  
Kirk K. S. Hwang ◽  
K. S. Wu ◽  
P. E. Gibson ◽  
...  
Keyword(s):  
Block Copolymers ◽  
Hard Segment ◽  
Length Distribution ◽  
Segment Length

scholarly journals Modification of epoxy resins with thermoplastic segmented polycarbonate-based polyurethanes

2014 ◽  
Vol 68 (6) ◽  
pp. 755-765 ◽  
Author(s):  
Jelena Pavlicevic ◽  
Mirjana Jovicic ◽  
Vesna Simendic ◽  
Oskar Bera ◽  
Radmila Radicevic ◽  
...  
Keyword(s):  
Tensile Strength ◽  
Epoxy Resin ◽  
Hard Segment ◽  
Crosslinking Agent ◽  
Polyurethane Elastomers ◽  
Hard Segment Content ◽  
Weight Content ◽  
Epoxy Curing ◽  
Hard Segments ◽  
Modified Epoxy

In this work, epoxy hybrid materials were synthesized by addition of thermoplastic segmented aliphatic polyurethanes with good elastic properties. The modified epoxy samples were obtained by curing of previously homogenized mixture of prepared polyurethane melts, epoxy resin and crosslinking agent Jeffamine D-2000. The influence of different weight content of polyurethanes (5, 10 and 15 wt. % compared to pure epoxy resin) as well the influence of different hard segments of elastomers (20, 25 and 30 wt. %) on the curing of modified epoxy systems was studied. The curing was followed by differential scanning calorimetry (DSC), in dynamic regime from 30 to 300?C, at three heating rates (5, 10 and 20?C/min). With the increase of hard segments content of polyurethanes added in higher concentration (10 and 15 wt. %) into epoxy matrix, the temperature of maximum ratio of curing was shifted to lower values (from 205 to 179?C). Obtained DSC data were analyzed using two integral methods (Ozawa-Flynn-Wall and Kissinger-Akahira-Sunose) and one differential kinetic model (Friedman). The significant differences were observed in the second part of the epoxy curing (for the reaction degrees higher than 60 %), where the values of activation energies remarkably increase. The addition of polyurethane elastomers retarded the curing process due to decreased mobility of reactant molecules caused by higher viscosity of reaction mixture. By detailed analysis of determined kinetic parameters, it is concluded that the influence of slow diffusion is more pronounced in the presence of thermoplastic polycarbonate-based polyurethanes, which confirmed their effect on the mechanism of epoxy curing. The highest tensile strength and hardness showed the DGEBA modified with the polyurethane with highest hard segment content. Increasing the hard segment content of polyurethane and its concentration in matrix, the tensile strength of modified epoxy was increased. The elongation at break of modified epoxy samples was significantly improved by addition of polycarbonate-based polyurethanes with low hard segment content, due to higher content of flexible soft segment chains.

Synthesis of urea-containing ABA triblock copolymers: Influence of pendant hydrogen bonding on morphology and thermomechanical properties

2018 ◽  
Vol 56 (16) ◽  
pp. 1844-1852
Author(s):  
Mingtao Chen ◽  
David L. Inglefield ◽  
Keren Zhang ◽  
Amanda G. Hudson ◽  
Samantha J. Talley ◽  
...  
Keyword(s):  
Hydrogen Bonding ◽  
Triblock Copolymers ◽  
Thermomechanical Properties
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