UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

FORM 8-K

CURRENT REPORT

Pursuant to Section 13 or 15(d) of

The Securities Exchange Act of 1934

Date of Report (Date of earliest event reported) February 10, 2016

NANOPHASE TECHNOLOGIES CORPORATION

(Exact name of registrant as specified in its charter)

Registrant’s telephone number, including area code: (630) 771-6700

(Former name or former address, if changed since last report)

Check the appropriate box below if the Form 8-K filing is intended to simultaneously satisfy the filing obligation of the registrant under any of the following provisions:

On February 10, 2016, Nanophase Technologies Corporation (the “Company”) entered into a Common Stock Purchase Agreement (the “Common Stock Purchase Agreement”) with Bradford T. Whitmore (the “Investor”) pursuant to which the Investor purchased 2,600,000 shares of the Company’s common stock, $0.01 par value (“Common Stock”), at a price of $0.38 per share for an aggregate price of $988,000. The Company agreed to provide to the Investor certain demand registration rights in respect of the shares of Common Stock at any time four years after the date of the Common Stock Purchase Agreement and certain customary piggyback registration rights in respect of the shares of Common Stock at any time after the date of the Common Stock Purchase Agreement. The Common Stock Purchase Agreement contains customary terms and conditions, including certain customary indemnification obligations.

The foregoing description of the Common Stock Purchase Agreement does not purport to be complete and is subject to, and qualified in its entirety by, the full text of the Common Stock Purchase Agreement, which is attached hereto as Exhibit 4.1, and is incorporated herein by reference.

Prior to the entry into the Common Stock Purchase Agreement, the Investor owned approximately 37% of the Company’s outstanding Common Stock. The Investor’s sister, R. Janet Whitmore, has served on the Company’s Board of Directors since 2003.

The information contained in Item 1.01 of this Current Report on Form 8-K is incorporated herein by reference.

As described in Item 1.01, on February 10, 2016, the Company issued to the Investor 2,600,000 shares of Common Stock for an aggregate purchase price of $988,000. The Company intends to use the proceeds from the sale for working capital and general corporate purposes. This issuance and sale is exempt from registration under the Securities Act of 1933, as amended (the “Securities Act”), under Section 4(a)(2) of the Securities Act and Regulation D thereunder. The Investor has represented to the Company that he is an “accredited investor” as defined in Rule 501 of the Securities Act and that the Common Stock is being acquired for investment purposes and not with a view to or for sale in connection with any distribution thereof. Appropriate legends have been affixed to the certificates evidencing the shares of Common Stock. No selling commission or other remuneration was paid in connection with the issuance of the Common Stock.

SIGNATURE

Pursuant to the requirements of the Securities Exchange Act of 1934, the Registrant has duly caused this report to be signed on its behalf by the undersigned hereunto duly authorized.