Effect of Soft Segment Length and Chain Extender Structure on Phase Separation and Morphology in Poly(urethane urea)s

Abstract

The phase separation and morphology in poly(urethane urea)s were investigated as soft segment length and chain extender structure were varied. Increases in soft segment length led to increased phase separation that resulted in greater mobility of the soft segment. This was shown by lower soft segment glass transition temperatures in differential scanning calorimetry (DSC) as well as a shift of Emax″ and tan δmax to lower temperatures. Also the structure of the chain extender affected the degree of phase separation and mixing of the soft and the hard blocks in an interphase. Atomic force microscopy (AFM) was used to visualize the structure of the phase‐separated domains. The hard domains were in the form of spheres 5–10 nm, or long needles 5 nm thick and 50–300 nm long. As the soft segment length increased, there were more pure soft segment phase areas between the hard domains. At high hard segment content, a larger scale structure was found, consisting of both hard and soft segments.DSC thermograms of poly(urethane urea)s containing different soft segment lengths.magnified imageDSC thermograms of poly(urethane urea)s containing different soft segment lengths.

Synthesis and characterization of fluorocarbon chain end‐capped poly(carbonate urethane)s as biomaterials: A novel bilayered surface structure

“…Many researchers 31,[34][35][36][37][38] assigned the bright region to hard blocks and dark region to soft blocks. However, Magonov et al 39 observed contrast inversion in phase images by reducing r sp .…”

Synthesis, phase behavior, and simulated in vitro degradation of novel HTPB-b-PEG polyurethane copolymers

“…This is mainly due to a restricted mobility of the soft segments for short molecular chains. 11 As the temperature is raised, an exothermic peak appears at about 0-5 o C for the block copolymers with the MW of PEG lower than 2,000. This transition is generally referred to "cold crystallization" of the soft segments, which is a result of the rearrangement and ordering of nearby segments in the amorphous regions of the PUs.…”

“…[6][7][8][9][10] The microphase separation of PUs is greatly influenced by the miscibility of the starting compounds, the structure and the molar mass distribution of the segments, the average block lengths, and the ratio of hard to soft segments. 11 Many methods, for example, polarized optical microscope (POM), scanning electron microscope (SEM), dynamic mechanical analysis (DMA), small angle X-ray scattering (SAXS), [12][13][14][15][16] atomic force microscopy (AFM), 11,17 differential scanning calorimetry (DSC), 18 Fourier transform infrared spectra (FTIR) 19 and nuclear magnetic resonance (NMR) 20 etc., have been used to probe the microphase separation. Since the microphase separation and the phase morphology have an important influence on the ultimate properties of the PU copolymers, it is desirable to have a control on the microphase separation in PUs.…”

Biodegradable Polyurethanes and Poly(ester amide)s

“…PURs prepared from MDI, 1,3 -PDA, and a poly(caprolactone) diol of a M n molecular weight of 530 have been found suitable since they exhibit high tensile strength, a high modulus, and retention of mechanical properties when degraded adequately to the time required for the application [16,44]. (ii) Meniscal and fi brocartilage reconstruction.…”