Structure–property relationships of poly(urethane urea)s with ultra‐low monol content poly(propylene glycol) soft segments. I. Influence of soft segment molecular weight and hard segment content

Abstract

Structure-property relationships in poly(urethane urea)s synthesized with ultra-low monol content poly(propylene glycol) soft segments were investigated as soft segment molecular weight (2000, 4000, and 8000 g/mol) and hard segment content (6.3 and 9.0 wt %) were varied. Morphological features such as interdomain spacing and interphase thickness were quantified and revealed with small-angle X-ray scattering (SAXS) and atomic force microscopy (AFM). The thermal and mechanical behavior was assessed with a dynamic mechanical analyzer (DMA) and by differential scanning calorimetry (DSC) and stress-strain tests. Hard segment content, over the limited range studied, had little effect on the morphology and soft segment thermal and mechanical properties. The molecular weight of the soft segments had considerably more influence on the morphology and mechanical properties. Increasing soft segment molecular weight resulted in greater interdomain spacings, as shown by SAXS, and a noticeable change in the structure, as shown by AFM. Additionally, as soft segment molecular weight decreased the soft segment glass transition broadened and rose to higher temperatures.

Development and characterization of magnetorheological elastomers

“…Thus, for the imaged PUs, the microdomains appear lighter whereas darker regions correspond to the softer polyol phase. 16,17 Figure 21 shows the microphase of polybutadiene-PU. The existence of brighter areas demonstrated that the hard and soft segments did not possess homogeneous features and demonstrated phase separation in the PU elastomer.…”

“…16 The thermal properties of MRE were also investigated by step-scan DSC. A comparison of MREs and PU elastomers is provided in Figure 18.…”

Polyurethanes with Narrow‐ and Polydisperse Hard Segment Distributions

“…First, a soft segment (SS) prepolymer, end-capped with diisocyanate is prepared with excess diisocyanate. [11][12][13] This prepolymer is subsequently extended with an extender and possibly also additional diisocyanate. For thermoplastic elastomer applications, the diisocyanate, MDI 4,4 0 methylenebis(phenyl isocyanate) is often used, and in order to obtain copolymers with good low temperature properties, poly(propylene oxide) (PPO) is generally employed since PPO is noncrystalline.…”

“…[14] When an MDIendcapped prepolymer with a low concentration of free MDI is reacted with a diamine, the result is urethane-urea HS with a narrow length distribution. [12] If additional MDI is added together with the diamine, the HS length distribution becomes random. [13] Generally, the melting temperature of the HSs increases rather significantly as their length increases.…”

Synthesis of Collagenase‐Sensitive Polyureas for Ligament Tissue Engineering

“…[17][18][19] Factors that influence the degree of phase separation include soft segment molecular weight, hard and soft segment chemistries, and the hard to soft segment ratio. [20][21][22][23][24] Segmented block copolymers utilized for biomedical applications have traditionally been intended for long-term use. Thus, new biodegradable formulations are needed to translate this family of biomaterials to tissue engineering applications.…”