Tuning nanophase separation behavior in segmented polyhydroxyurethane via judicious choice of soft segment

Abstract

based soft segments, with divinyl benzene dicyclocarbonate and Dytek-A as hard segment and chain extender, respectively. These NIPU polymers were characterized by small-angle X-ray scattering (SAXS), atomic force microscopy (AFM), dynamic mechanical analysis (DMA), differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FTIR) and tensile testing. SAXS reveals that the NIPUs with 30-40 wt% hard segment are nanophase separated with interdomain spacings of 9-16 nm. DMA reveals that PTMO-based PHUs have broad interphases with a range of local compositions and glass transition temperatures (T g s), with tan δ ≥ 0.3 over temperature ranges exceeding 70 °C in breadth. In contrast, PBN-based PHUs have sharper interphases, evidenced by narrow tan δ peaks near soft-segment and hard-segment T g s as well as by DSC and AFM data. FTIR shows that the ratio of hydrogen-bonded carbonyl to free carbonyl

Tuning the properties of segmented polyhydroxyurethanes via chain extender structure

“…Most previous PHU studies have focused on the synthesis of cyclic carbonate monomers and their subsequent polymerization into single‐phase thermoplastics or crosslinked thermosets, or on catalysis of the cyclic carbonate aminolysis reaction . Few studies have investigated segmented, nanophase‐separated PHU and established an understanding of their structure–property relationships . Leitsch et al .…”

“…Beniah et al . have also demonstrated that nanophase separation in PHUs can be significantly tuned via judicious choice of soft segment . Despite these advances, segmented PHUs exhibit generally inferior thermal and mechanical properties relative to isocyanate‐based, segmented PU .…”

Functionalization of hydroxyl groups in segmented polyhydroxyurethane eliminates nanophase separation

“…The DMA results for PHU‐Ac reflect the characteristic of single‐phase polymeric material and show that hydroxyl group functionalization with an acetyl group results in loss of nanophase separation despite the absence of hydroxyl groups which participate significantly in intersegmental hydrogen bonding in PTMO‐based PHU . Thus, although elimination of intersegmental hydrogen bonding in PHU by using polybutadiene‐based soft segment leads to excellent nanophase separation with narrow interphase, the elimination of hydroxyl groups necessary for such intersegmental hydrogen bonding in PTMO‐based PHU by functionalization with acetic anhydride results in the loss of nanophase separation itself.…”

“…The nanophase separation in PTMO‐based PHU is accompanied with broad interphase, which is due to a significant level of intersegmental hydrogen bonding between the hydroxyl groups to the soft segment . When a soft segment with no potential for intersegmental hydrogen bonding is used, such as polybutadiene‐based soft segment, nanophase‐separated PHUs with a much sharper domain interphase like that exhibited by conventional thermoplastic PU elastomer are obtained . Recently, Torkelson et al also reported that incorporating amide‐based, diamine diamide chain extender results in significant improvement in nanophase separation and properties of PHUs .…”

Stimuli‐Responsive Polyurethane Dispersions – Aqueous Auto‐Dispersion

“…[13] Glass transition temperatures and mechanical properties such as hardness and flexibility can be tailored by incorporation of soft and hard segments and through careful selection of polyols. [14,15] These segments also affect amounts of crystalline and amorphous structures developed and provide both abrasion and solvent resistance.…”