Exhibit 4.26

FOURTH AMENDMENT TO PROMISSORY NOTE

ISSUED DECEMBER 17, 2009

THIS AMENDMENT (the Amendment) is made as of the 28thday of February, 2011 (the Effective Date), by and
between Platinum -Montaur Life Sciences LLC, a Delaware limited liability company, with an address of 152 West
57thStreet, 54thFloor, New York, N.Y. 10018 (Holder) and Dais Analytic
Corporation having an office at 11552 Prosperous Drive, Odessa, Florida 33556 (Maker). (Each individually referred to herein as Party and together as Parties).

WITNESSETH

WHEREAS, on December 17, 2009, Maker issued to Holder an unsecured promissory note in the principal amount of One Million
Dollars ($1,000,000) (Note); and

WHEREAS, the Parties have amended the Note setting the Maturity Date (as
defined in said Note) at February 28, 2011; and

WHEREAS, the Parties desire to further amended the Note to extend
Maturity Date thereof to April 30, 2011; and

NOW, THEREFORE, in consideration of the mutual premises,
representations, warranties, covenants and agreements contained herein, and intending to be legally bound hereby, the Parties hereto agree as follows:



|1. | The following paragraph of the Note, as amended, is hereby deleted in its entirety:
|-- | -----------------------------------------------------------------------------------

All payments under or pursuant to this Note shall be made in United States Dollars in immediately available funds to the Holder at
the address of the Holder first set forth above or at such other place as the Holder may designate from time to time in writing to the Maker or by wire transfer of funds to the Holders account, as requested by the Holder. The outstanding
principal balance of this Note, together with all accrued and unpaid interest, shall be due and payable in full on February 28, 2011(the Maturity Date) or at such earlier time as provided herein.



|2. | The following provision is hereby inserted in place of the paragraph deleted pursuant to Section 1 of this Amendment:
|-- | ---------------------------------------------------------------------------------------------------------------------

All payments under or pursuant to this Note shall be made in United States Dollars in immediately available funds to the Holder at
the address of the Holder first set forth above or at such other place as the Holder may designate from time to time in writing



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|Page 1 of 2 |  | Fourth Amendment to Promissory Note |  | Platinum Montaur /Dais
|            |  | Issued December 17, 2009            |  |                       



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to the Maker or by wire transfer of funds to the Holders account, as requested by the Holder. The outstanding principal balance of this Note, together with all accrued and unpaid interest,
shall be due and payable in full on April 30, 2011 (the Maturity Date ) or at such earlier time as provided herein.



|3. | Section 2.3 of the Note, as amended, is hereby deleted in its entirety and the following provision shall be inserted in place thereof:
|-- | --------------------------------------------------------------------------------------------------------------------------------------

Section 2.3. Additional Remedy Upon Non-Payment. If this Note is not paid in full on or before April 30, 2011, the
Holder shall be permitted, at its sole option and in addition to its other remedies hereunder, to convert the principal and interest outstanding under this Note into any debt, equity or equity-linked security issued by the Maker in connection with
any capital-raising issuance after the date hereof and prior to the date this Note is paid in full on the terms and conditions of such offering, if any, it being understood that (i) nothing in this Section 2.3 shall be deemed to prohibit
the Maker from prepaying the Note pursuant to Section 1.2 hereof and (ii) in connection with any such conversion, the security issued to the Holder shall contain customary 9.9% beneficial ownership limitations in form and substance
satisfactory to the Holder.



|4. | All other terms and conditions of the Note shall remain unchanged and in full force and effect.
|-- | -----------------------------------------------------------------------------------------------

IN WITNESS WHEREOF, the Parties have caused this Amendment to be executed by their duly authorized respective representatives as
of the date first written above.



|                                    |  |                                     
|----------------------------------- |  | ------------------------------------
|DAIS ANALYTIC CORPORATION          
|                                    | 
|By:                                 |  | /s/ Timothy N. Tangredi             
|                                    | 
|Name:                               |  | Timothy N. Tangredi                 
|                                    | 
|Title:                              |  | President and Chief Executive Office
|                                   
|PLATINUM-MONTAUR LIFE SCIENCES, LLC
|                                    | 
|By:                                 |  | /s/ Joseph Firestone                
|                                    | 
|Name:                               |  | Joseph Firestone                    
|                                    | 
|Title:                              |  | Associate                           



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|Page 2 of 2 |  | Fourth Amendment to Promissory Note |  | Platinum Montaur /Dais
|            |  | Issued December 17, 2009            |  |