Thermoreversible Polyurea

Patent Title: DYNAMIC UREA BONDS FOR POLYMERS

 Number/Link: W02016/069582

Applicant/Assignee: University of Illinois

Publication date: 6-05-2016

Gist”: Urea bonds prepared from sterically hindered amines and isocyanates

Why it is interesting: The N-C bond in urea is very stable due to conjugation of the lone electron pair of the nitrogen atom with the cabonyl group.  According to this invention, the nitrogen atom can be subsituted with a strongly hindering group such that the coplanarity, and therefore most of the conjugation, of the C-N and C=O bonds is lost. These hindered urea bonds are much less stable and can reversibly depolymerize at relatively low temperatures. Thermoreversible bonds can be useful in a number of smart materials such as self-healing-, “4D printing”- , and reprogrammable shape memory materials. In an example a shape memory material with a Tg of 53°C and a Young’s Modulus of about 2 GPa was prepared by reacting 2-(t-buylamino)ethanol (TBAE) and trimerized hexamethylene diisocyanate (THDI). The ‘permanent shape’ of the material could be re-programmed by forcing the material in a new shape for 72 hours at 60°C.

Polurethane-urea with thermoreverisble urea bonds

Poly(urethane-urea) with thermoreverisble urea bonds

SHSM Polyurethanes

Title: SHAPE-MEMORY-SELF-HEALING POLYMERS (SMSHPS)

 Number/Link: WO2015119688

Applicant/Assignee: University of Florida

Publication date: 13-08-2015

Gist”: Self-healing shape memory polyurethanes made by incorporation of DA adducts in-chain

Why it is interesting: According to this invention self-healing shape memory polyurethanes can be prepared by incorporating Diels-Alder (DA) adducts into the PU network such that the DA adducts do not contribute to the crosslinking.  In this manner the material can be heated above Tg without breaking crosslinks thereby inhibiting permanent distortion of the memorised shape. The Tg is also chosen such that it is lower than the temperature at which the retro-DA reaction readily occurs. The DA adducts can be introduced using a DA adduct-containing diol as for example the adduct of a furfuryl alcohol and N-(2-hydroxyethyl)maleimide.  The SHSM polyurethanes are said to be useful for coatings and moulded materials.

Diol containing a Diels-Alder adduct

Diol containing a Diels-Alder adduct

Hydrophobic and Clear Thermoplastic Polyurethane

Title: CLEAR HYDROPHOBIC TPU

 Number/Link: WO2014/121174

Applicant/Assignee: Lubrizol

Publication date: 7-08-2014

Gist”: A hydrophobic, clear and low density TPU is prepared from 4,4’MDI, a dimer acid-based polyol and a mixture of “non-stacking” chain extenders.

Why it is interesting: Most commercial TPUs are hydrophilic to a certain extend and because of phase separation and partial crystallization are often transparent but not clear. The current invention teaches a highly hydrophobic and clear TPU made form 4,4′ MDI, a polyester polyol produced by reacting a C36 dimerized fatty acid (“dimer acid”) with 1,6-hexanediol and a chain extender mixture consisting of 1,12-dodecanediol and 2-butyl,2-ethyl propanediol or  1,4-cyclohexanedimethanol (all preferred). Hardblock content in the examples is between 25 and about 45% resulting in a shore A hardness range of about 75 to 95. No thermal data are given.
While this is no doubt an interesting material, I expect this to be a single phase glass with a relatively low Tg and therefore less useful for structural applications.

Example of a C36 dimer acid

Example of a C36 dimer acid

 

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