<PAGE>

                                                                     EXHIBIT 4.2


                         COMMON STOCK PURCHASE AGREEMENT
                         -------------------------------

         THIS COMMON STOCK PURCHASE AGREEMENT (the "Agreement") is made and
entered into as of July 1, 2003, by and among ACACIA RESEARCH CORPORATION, a
Delaware corporation (the "Purchaser") and the individuals set forth on the
signature page hereto (each, a "Seller" and, collectively the "Sellers").
Capitalized terms used herein shall have the meanings set forth in Article 5.


                                R E C I T A L S :
                                - - - - - - - -


         WHEREAS, the Seller desires to sell to the Purchaser, and the Purchaser
desires to purchase from the Seller, shares of the Common Stock of Advanced
Material Sciences, Inc., a Delaware corporation ("AMS"), for the consideration
set forth herein.

         WHEREAS, capitalized terms used herein and not otherwise defined shall
have the meanings set forth in Section 5.1.

         NOW, THEREFORE, in consideration of the mutual promises and agreements
herein, and subject to the terms and conditions hereinafter set forth, the
parties hereby agree as follows:

                                   ARTICLE 1

                           PURCHASE AND SALE OF SHARES

         1.1 PURCHASE AND SALE. On the basis of the representations, warranties,
covenants and agreements and subject to the satisfaction or waiver of the terms
and conditions, set forth herein, each Seller agrees to sell to the Purchaser
and the Purchaser agrees to purchase from each Seller that number of shares of
common stock of AMS (collectively the "AMS Shares") set forth next to such
Seller's name on the signature page hereto in exchange for that number of shares
of the Purchaser's Acacia Research-CombiMatrix Common Stock (collectively the
"Acacia Shares") set forth next to such Seller's name on the signature page
hereto.

         1.2 THE CLOSING OF PURCHASE AND SALE OF COMMON STOCK. The purchase and
sale described in Section 1.1 shall take place at a closing (the "Closing") to
be held at the offices of the Purchaser, 500 Newport Center Drive, Suite 700,
Newport Beach, California 92660, on July 1, 2003. At the Closing, the Sellers
shall convey and deliver stock certificate(s), duly endorsed for transfer to the
Purchaser or accompanied by a duly executed stock assignment separate from
certificate, evidencing the AMS Shares against delivery by Purchaser to Sellers
of stock certificates representing the Acacia Shares.

<PAGE>

                                   ARTICLE 2

                   REPRESENTATIONS AND WARRANTIES BY PURCHASER

         The Purchaser represents, warrants, agrees, and covenants as follows:

         2.1 AUTHORIZATION.

                  (a) The Purchaser is duly authorized to execute and deliver
this Agreement and instruments executed in connection herewith.

                  (b) The Purchaser is a duly organized and validly existing
corporation in good standing under the laws the State of Delaware and has all
requisite corporate power and authority for the ownership and operation of its
properties and for the carrying on of its business as now conducted and as
proposed to be conducted. The Purchaser is duly licensed or qualified and in
good standing as a foreign corporation authorized to do business in all
jurisdictions in which the nature of the respective business conducted or
property owned by it makes such qualification necessary.

                  (c) This Agreement and each other agreement and instrument
contemplated hereby constitute the valid and binding obligations of the
Purchaser, enforceable against it in accordance with their respective terms,
except as may be limited by bankruptcy, insolvency, reorganization, moratorium
or similar laws relating to or affecting creditors' rights generally.

                  (d) The execution, delivery and performance of this Agreement
will not breach, violate or conflict with its Restated Certificate of
Incorporation or Amended and Restated Bylaws or any material agreement to which
Purchaser is a party or by which it is bound.

                  (e) Other than consents or approvals under state and federal
securities laws, rules and regulations, no consent or approval of any Person (as
defined in Section 5.1 below) is required in connection with the execution,
delivery and performance of this Agreement and such other agreements and
instruments by the Purchaser which has not heretofore been obtained.

         2.2 ACACIA SHARES. The Acacia Shares have been duly authorized, are
validly issued and are fully paid and nonassessable.

         2.3 OTHER. No Person has or will have, as a result of the transactions
contemplated by this Agreement, any right, interest or valid claim upon or
against the Sellers for any commission, fee or other compensation as a finder or
broker because of any act or omission by such Purchaser and the Purchaser agrees
to indemnify and hold the Sellers harmless against any such commissions, fees or
other compensation.

                                      -2-
<PAGE>

                                   ARTICLE 3

                    REPRESENTATIONS AND WARRANTIES OF SELLER

         Each Seller represents, warrants, and covenants as follows:

         3.1 NO SOLICITATION. The Agreement was in no way a result of a
solicitation of the Seller by the Purchaser. The transactions contemplated by
this Agreement resulted from an unsolicited offer by the Sellers to exchange
their AMS Shares for the Acacia Shares.

         3.2 DUE DILIGENCE EXAMINATION. Each Seller and his advisers have relied
on their own examination of reports filed by the Purchaser under the Securities
Act, the Exchange Act and other publicly available information relating to the
Purchaser and the Purchaser's business and finances (collectively, the
"Information"), and any and all other information deemed relevant by the Seller
in order to make an informed investment decision regarding this Agreement, and
have reviewed and received such Information and understand the Information and
this Agreement. Without limiting the foregoing, each Seller acknowledges that it
has received and reviewed the following:

                  (a) the Purchaser's proxy statement, dated November 8, 2002;

                  (b) the Purchaser's Annual Report on Form 10-K for the year
ended December 31, 2002;

                  (c) the Purchaser's Quarterly Report on Form 10-Q for the
quarter ended March 31, 2003; and

                  (d) the Purchaser's proxy statement, dated April 10, 2003.

         3.3 SOPHISTICATION. Each Seller has such knowledge and experience in
financial, tax, and business matters so as to enable such Seller to utilize the
information made available to the undersigned in connection with this Agreement
to evaluate the merits and risks of such and to make an informed investment
decision with respect thereto. No Seller is relying on the Purchaser with
respect to the legal, tax, and other economic considerations of this Agreement
and has obtained, or had the opportunity to obtain the advice of such Seller's
own legal, tax and other advisors.

         3.4 COOPERATION. Each Seller hereby agrees to provide such information
and to execute and deliver such documents as may reasonably be necessary to
comply with any and all laws and ordinances to which the Purchaser is subject,
including, without limitation, such additional information as the Purchaser may
deem appropriate with regard to such Seller's suitability.

         3.5 GOOD AND MARKETABLE TITLE. Each Seller has, and at the Closing, the
Purchaser will receive, good and marketable title to the AMS Shares owned by
such Seller, free and clear of all liens, claims, security interests, charges
and encumbrances.

                                      -3-
<PAGE>

         3.6 AUTHORITY; ENFORCEABLE AGREEMENTS.

                  (a) Each Seller has full legal capacity and authority to enter
into, execute and deliver this Agreement and each other agreement and instrument
executed in connection herewith.

                  (b) This Agreement and such other agreements and instruments
contemplated hereby constitute the valid and binding obligations of each Seller,
enforceable against each Seller in accordance with their respective terms,
except as may be limited by bankruptcy, insolvency, reorganization, moratorium
or similar laws relating to or affecting creditors' rights generally.

                  (c) The execution, delivery and performance of this Agreement
will not breach, violate or conflict with any agreement to which any Seller is a
party or by which it is bound.

                  (d) No consent or approval of any Person is required in
connection with the execution, delivery and performance of this Agreement or any
other agreements and instruments by which any of the Sellers is bound which has
not heretofore been obtained.

         3.7 INVESTMENT. Each Seller is acquiring the Acacia Shares for
investment for his, her or its own account, and not with the view to, or for
resale in connection with, any "distribution" of all or any portion thereof
within the meaning of the Securities Act. The Acacia Shares received by the
Seller will be restricted securities. Each Seller understands that the Acacia
Shares to be acquired hereunder have not been registered under the Securities
Act by reason of a specific exemption from the registration provisions of the
Securities Act which depends upon, among other things, the bona fide nature of
the Sellers' investment intent and the accuracy of the Sellers' representations
as expressed herein. No Seller has offered or sold any portion of the Acacia
Shares being acquired nor does any Seller have any contract, understanding,
agreement or arrangement with any person or with respect to any portion of the
Acacia Shares. Each Seller acknowledges that the Acacia Shares being acquired
hereunder must be held indefinitely unless the transfer thereof is registered
under the Securities Act or unless an exemption from such registration is
available, and that each share certificate representing the Acacia Shares shall
bear a legend setting forth the restrictions on the transfer thereof
substantially in the following form:

                  "THIS SECURITY HAS NOT BEEN REGISTERED UNDER THE SECURITIES
                  ACT OF 1933, AS AMENDED (THE "ACT"), OR APPLICABLE STATE
                  SECURITIES LAWS AND MAY NOT BE TRANSFERRED OR OTHERWISE
                  DISPOSED OF UNLESS IT HAS BEEN REGISTERED UNDER THE ACT AND
                  SUCH LAWS OR (1) REGISTRATION UNDER SUCH LAWS IS NOT REQUIRED
                  AND (2) AN OPINION OF COUNSEL SATISFACTORY TO THE COMPANY IS
                  FURNISHED TO THE COMPANY TO THE EFFECT THAT REGISTRATION UNDER
                  THE ACT AND THE APPLICABLE STATE SECURITIES LAWS IS NOT
                  REQUIRED."

                                      -4-
<PAGE>

Each Seller is an "accredited investor" as defined in Rule 501 under the
Securities Act. In connection with the foregoing, each Seller has delivered to
Purchaser a completed and executed a Confidential Purchaser Questionnaire in the
form attached hereto as Schedule 1.

         3.8 RULE 144. Each Seller acknowledges that he, she or it is aware of
the provisions of Rule 144 promulgated under the Securities Act which permit
limited resale of shares purchased in a private placement, subject to the
satisfaction of certain conditions, including, among other things, the
availability of certain current public information about the Purchaser, the
resale occurring after the expiration of minimum holding periods after a party
has purchased and paid for the security to be sold, the sale being effected
through a "broker's transaction" or in transactions directly with a "market
maker" and the number of shares being sold during any three-month period not
exceeding specified limitations except as provided in Rule 144(k).

         3.9 INDEMNIFICATION. Each Seller agrees, jointly and severally, to
indemnify and hold harmless the Purchaser against and in respect of any loss,
liability, damage, claim or expense resulting from any breach of any
representation, warranty, covenant or agreement by him, her or it contained in
this Agreement.

         3.10 ACACIA RESEARCH--COMBIMATRIX STOCK. Each Seller acknowledges that
the Purchaser's Acacia Research-CombiMatrix common stock, including the Acacia
Shares, and the Purchaser's Acacia Research-Acacia Technologies common stock are
both classes of common stock of the Purchaser, and as such remain subject to all
risks associated with an investment in the Purchaser and all of Purchaser's
businesses, assets and liabilities. Each Seller further acknowledges that
although the Acacia Research-CombiMatrix common stock and the Acacia
Research-Acacia Technologies common stock are intended to reflect the
performance of different business groups within the Purchaser, they are not
stock issued by the separate groups and accordingly the market values of the two
classes may not in fact reflect the performance of the separate groups.

         3.11 OTHER. No person has or will have, as a result of the transactions
contemplated by this Agreement, any right, interest or valid claim upon or
against the Purchaser for any commission, fee or other compensation as a finder
or broker because of any act or omission by any Seller and the Sellers agree,
jointly and severally, to indemnify and hold the Purchaser harmless against any
such commissions, fees or other compensation.

                                   ARTICLE 4

                REGISTRATION RIGHTS WITH RESPECT TO ACACIA SHARES

         4.1 REGISTRATION RIGHTS.

                  (a) REGISTRATION. The Purchaser will file a Registrations
Statement with the SEC for the resale of the Acacia Shares within sixty (60)
days of the date hereof. Subject to the provisions of this Agreement, the
Purchaser shall use its reasonable efforts to cause such Registration Statement
to be declared effective by the SEC as promptly as shall be practicable.
Purchaser shall use its best efforts to keep such Registration Statement in
effect until Sellers have sold or otherwise distributed all of the Acacia Shares
or until such Acacia Shares may be traded without restriction pursuant to

                                      -5-
<PAGE>

paragraph (k) of Rule 144, if applicable. Purchaser acknowledges and agrees that
time is of the essence with respect to the liquidity of the Acacia Shares.
Sellers shall promptly notify the Purchaser of the proposed manner of sale of
any Acacia Shares to be sold pursuant to such Registration Statement other than
in an unsolicited brokers' transaction including only usual and customary
brokers' commissions. No Seller shall undertake any such transactions other than
unsolicited brokers' transaction including only usual and customary brokers'
commissions unless (i) such Seller shall have furnished all information required
to be disclosed in any related prospectus supplement, and (ii) such Seller shall
have agreed in writing to bear all costs of registration and related expenses
(including attorneys' fees).

                  (b) SUSPENSION OF EFFECTIVENESS. The Purchaser's obligations
under Section 4.1 (a) above shall not restrict its ability to suspend the
effectiveness of, or direct any Seller not to offer or sell securities under,
the Registration Statement, at any time, for such reasonable period of time
which the Purchaser believes is necessary to prevent the premature disclosure of
any events or information having a material effect on the Purchaser. In
addition, the Purchaser shall not be required to keep the Registration Statement
effective, or may, without suspending such effectiveness, instruct any Seller
not to sell such securities, during any period during which the Purchaser is
instructed, directed, ordered or otherwise requested by any governmental agency
or self-regulatory organization to stop or suspend such trading or sales.

                  (c) HOLDBACK AGREEMENT. In the event of any filing of a
prospectus supplement or the commencement of an underwritten public distribution
of the Purchaser's Common Stock under a Registration Statement, each Seller
agrees not to effect any public sale or distribution of the Purchaser's Common
Stock, including a sale pursuant to Rule 144 or Rule 144A under the Securities
Act, during a period designated by the Purchaser in a written notice duly given
to the Sellers, which period shall commence approximately 14 days prior to the
effective date of any such filing of such prospectus supplement or the
commencement of such underwritten public distribution of such Purchaser's Common
Stock under a Registration Statement and shall continue for up to 180
consecutive days.

                  (d) REGISTRATION PROCEDURES. Except as otherwise expressly
provided herein, in connection with any registration of the Acacia Shares
pursuant to this Agreement, the Purchaser shall:

                  (i) furnish to each Seller one or more copies of the
         definitive final prospectus filed with the SEC;

                  (ii) notify the Sellers, at any time when a prospectus
         relating thereto is required to be delivered under the Securities Act,
         of the occurrence of any event as a result of which the prospectus
         included in such Registration Statement (including any document to be
         incorporated by reference therein) contains an untrue statement of a
         material fact or omits any fact necessary to make the statements
         therein not misleading and, at the request of any Seller, the Purchaser
         shall prepare a supplement or amendment to such prospectus so that, as
         thereafter delivered to the purchasers of such Acacia Shares, such
         prospectus will not contain an untrue statement of a material fact or
         omit to state any material fact required to be stated therein or
         necessary to make the statements therein not misleading and promptly
         make available to each Seller any such supplement or amendment; and

                                      -6-
<PAGE>

                  (iii) notify each Seller promptly, and (if requested by any
         such Person) confirm such advice in writing, (1) when the Registration
         Statement, the prospectus or any prospectus supplement or
         post-effective amendment has been filed, and, with respect to the
         Registration Statement or any post-effective amendment, when the same
         has become effective, (2) of the issuance by the SEC of any stop order
         suspending the effectiveness of a Registration Statement or of any
         order preventing or suspending the use of any preliminary prospectus or
         the initiation of any proceedings for that purpose and the Purchaser
         shall promptly use its reasonable best efforts to prevent the issuance
         of any stop order or to obtain its withdrawal if such stop order should
         be issued and (3) of the receipt by the Purchaser of any notification
         with respect to the suspension of the qualification or exemption from
         qualification of a Registration Statement or any of the Acacia Shares
         for offer or sale in any jurisdiction or the initiation or threatening
         of any proceeding for such purpose.

         The Purchaser may require each Seller to furnish to the Purchaser such
information regarding him, her or itself and the distribution of such Acacia
Shares as the Purchaser may from time to time reasonably request in writing and
such other information as may be legally required in connection with such
registration. Each Seller agrees, by his acquisition of the Acacia Shares and
his, her or its acceptance of the benefits provided to it hereunder, to furnish
promptly to the Purchaser all information required to be disclosed in order to
make any previously furnished information not materially misleading.

         Each Seller agrees, in connection with any disposition of the Acacia
Shares, to comply with all applicable prospectus delivery requirements of the
SEC. Each Seller further agrees that upon receipt of any notice from the
Purchaser of the happening of any event of the kind described herein requiring
the cessation of the distribution of a prospectus or the distribution of a
supplemented or amended prospectus, such Seller will forthwith discontinue
disposition of the Acacia Shares pursuant to the Registration Statement covering
such Acacia Shares until the Seller's receipt of the copies of the supplemented
or amended prospectus contemplated by this Agreement, or until it is advised in
writing by the Purchaser that the use of the prospectus may be resumed, and, if
so directed by the Purchaser, the Sellers will deliver to the Purchaser (at the
Purchaser's expense) all copies, other than permanent file copies then in the
Sellers' possession, of the prospectus covering such Acacia Shares current at
the time of receipt of such notice.

                  (e) REGISTRATION EXPENSES. All expenses incident to the
Purchaser's performance of or compliance with the registration of shares
pursuant to this Agreement, including, without limitation, all registration and
filing fees, fees and expenses of compliance with securities or blue sky laws,
fees and expenses of counsel for the Purchaser and its independent certified
public accountants, (all such expenses being herein called "Registration
Expenses") will be borne by the Purchaser; provided that in no event shall
Registration Expenses payable by the Purchaser include any (i) underwriting
discounts, commissions, or fees attributable to the sale of the Acacia Shares,
(ii) fees and expenses of any counsel, accountants, or other persons retained or
employed by any Seller, or (iii) transfer fees, if any.

                                      -7-
<PAGE>

                  (f) ASSIGNMENT OR TRANSFER. The rights granted to the Sellers
pursuant to this Article 4 shall not be, directly or indirectly, assigned, or
transferred.

                                   ARTICLE 5

                                   DEFINITIONS

         5.1 CERTAIN DEFINED TERMS. As used in this Agreement, the following
terms shall have the following meanings (such meanings to be equally applicable
to both the singular and plural forms of the terms defined):

                  "ACACIA SHARES" shall have the meaning assigned to that term
in Section 1.1 of this Agreement.

                  "AGREEMENT" means this Common Stock Purchase Agreement,
including all Schedules, as from time to time amended and in effect between the
parties hereto.

                  "AMS SHARES" shall have the meaning assigned to that term in
Section 1.1 of this Agreement.

                  "CLOSING" shall have the meaning assigned to that term in
Section 1.2 of this Agreement.

                  "EXCHANGE ACT" means the Securities Exchange Act of 1934, as
amended, and the rules and regulations thereunder, as shall be in effect at the
time.

                  "INFORMATION" shall have the meaning assigned to that term in
Section 3.2 of this Agreement.

                  "PERSON" means an individual, corporation, partnership,
limited liability company, joint venture, trust, or unincorporated organization,
or a government or any agency or political subdivision thereof.

                  "PURCHASER" shall have the meaning assigned to that term in
the preamble to this Agreement.

                  "REGISTRATION STATEMENT" means the registration statement or
comparable document under the Securities Act through which a public sale or
disposition of the Acacia Shares may be registered, including the prospectus,
amendments and supplements to such registration statement, all exhibits, and all
material incorporated by reference or deemed to be incorporated by reference in
such Registration Statement.

                  "SEC" means the Securities and Exchange Commission and
successors thereto.

                  "SECURITIES ACT" means the Securities Act of 1933, as amended,
and the rules and regulations thereunder, as shall be in effect at the time.

                                      -8-
<PAGE>

                  "SELLERS" shall have the meaning assigned to that term in the
preamble to this Agreement.

                                   ARTICLE 6

                                  MISCELLANEOUS

         6.1 NO WAIVER; CUMULATIVE REMEDIES. No failure or delay on the part of
the Purchaser in exercising any right, power or remedy hereunder shall operate
as a waiver thereof; nor shall any single or partial exercise of any such right,
power or remedy preclude any other or further exercise thereof or the exercise
of any other right, power or remedy hereunder. The remedies herein provided are
cumulative and not exclusive of any remedies provided by law.

         6.2 AMENDMENTS, WAIVERS AND CONSENTS. Any provision in this Agreement
to the contrary notwithstanding, no changes in or additions to this Agreement
may be made, and compliance with any covenant or provision herein set forth may
not be omitted or waived, without the prior written consent of the parties. Any
waiver or consent may be given subject to satisfaction of conditions stated
therein and any waiver or consent shall be effective only in the specific
instance and for the specific purpose for which given.

         6.3 ADDRESSES OR NOTICES, ETC. All notices, requests, demands and other
communications provided for hereunder shall be in writing (including telegraphic
communication) and mailed, by certified or registered mail, or telegraphed or
delivered to the applicable party at the addresses indicated below:

                  If to the Purchaser:

                           Acacia Research Corporation
                           500 Newport Center Drive
                           Suite 700
                           Newport Beach, California 92660
                           Attention:  Robert A. Berman, Senior Vice President
                                       and General Counsel

                  If to a Seller, to the address set forth below such Seller's
                  name on the signature page hereto.

         6.4 COSTS, EXPENSES AND TAXES. Each party shall pay its own fees in
connection with the investigation, preparation, execution and delivery of this
Agreement and other instruments and documents to be delivered hereunder and the
transactions contemplated hereby and thereby. In addition, each Seller shall pay
any and all material stamp and other taxes payable or determined to be payable
by such Seller in connection with the execution and delivery of this Agreement
and other instruments and documents to be delivered hereunder or thereunder, and
agrees to save the Purchaser harmless from and against any and all liabilities
with respect to or resulting from any delay in paying or omission to pay such
taxes and filing fees. In the event of any controversy, claim or dispute among
the parties hereto arising out of or relating to this Agreement, or any breach
hereof, the prevailing party shall be entitled to recover from the losing party
reasonable attorney's fees, expenses and costs.

                                      -9-
<PAGE>

         6.5 BINDING EFFECT; ASSIGNMENT. This Agreement shall be binding upon
and inure to the benefit of the Sellers and the Purchaser and their respective
successors and assigns.

         6.6 SURVIVAL OF REPRESENTATIONS AND WARRANTIES. All representations and
warranties made in this Agreement or any other instrument or document delivered
in connection herewith or therewith, shall survive the execution and delivery
hereof or thereof for a period of three (3) years from the date of this
Agreement.

         6.7 PRIOR AGREEMENTS. This Agreement constitutes the entire agreement
between the parties and supersedes any prior understandings or agreements
concerning the subject matter hereof.

         6.8 SEVERABILITY. The invalidity or unenforceability of any provision
hereto shall in no way affect the validity or enforceability of any other
provision.

         6.9 GOVERNING LAW. This Agreement shall be governed by, and construed
in accordance with, the laws of the State of California.

         6.10 JURISDICTION. Any suit, action or proceeding seeking to enforce
any provision of, or based on any matter arising out of or in connection with,
this Agreement or the transactions contemplated hereby may be brought in any
federal court located in Orange County, California or any California state court
located in Orange County, California, and each of the parties hereby consents to
the jurisdiction of such courts (and of the appropriate appellate courts
therefrom) in any such suit, action or proceeding and irrevocably waives, to the
fullest extent permitted by law, any objection that it may now or hereafter have
to the laying of the venue of any such suit, action or proceeding in any such
court or that any such suit, action or proceeding brought in any such court has
been brought in an inconvenient form. Process in any such suit, action or
proceeding may be served on any party anywhere in the world, whether within or
without the jurisdiction of any such court. Without limiting the foregoing, each
party agrees that service of process on such party as provided in Section 6.3
shall be deemed effective service of process on such party.

         6.11 WAIVER OF JURY TRIAL. EACH OF THE PARTIES HERETO HEREBY
IRREVOCABLY WAIVES ANY AND ALL RIGHT TO TRIAL BY JURY IN ANY LEGAL PROCEEDING
ARISING OUT OF OR RELATED TO THIS AGREEMENT, THE TRANSACTIONS CONTEMPLATED
HEREBY OR THE ACTIONS OF THE PARTIES HERETO IN THE NEGOTIATION, ADMINISTRATION,
PERFORMANCE AND ENFORCEMENT HEREOF.

         6.12 REPRESENTATION BY COUNSEL/GENERAL INTERPRETATION/MUTUAL
CONTRIBUTION. The parties hereto acknowledge that each party to this Agreement
is sophisticated and has been represented by counsel in connection with this
Agreement and the transactions contemplated by this Agreement, and that the
parties and their counsel have mutually contributed to the drafting of this
Agreement. Accordingly, no provision of this Agreement shall be construed
against any party on the ground that that party or its counsel draft the
provision or caused it to be drafted. No rule of strict construction will be
applied against any party. The provision of this Agreement shall be interpreted
in a reasonable manner to effect the intent of the parties.

                                      -10-
<PAGE>

         6.13 FACSIMILE SIGNATURES. Any signature page delivered by a fax
machine shall be binding to the same extent as an original signature page, with
regard to any agreement subject to the terms hereof or any amendments thereto.
Any party who delivers such a signature page agrees to later deliver an original
counterpart to any party which requests it.

         6.14 HEADINGS. Article, Section and subsection headings in this
Agreement are included herein for convenience of reference only and shall not
constitute a part of this Agreement for any other purpose.

         6.15 COUNTERPARTS. This Agreement may be executed in any number of
counterparts, all of which taken together shall constitute one and the same
instrument, and any of the parties hereto may execute this Agreement by signing
any such counterpart.

         6.16 FURTHER ASSURANCES. From and after the date of this Agreement,
upon the reasonable request of the Purchaser, each Seller shall execute and
deliver such instruments, documents and other writings as may be reasonably
necessary or desirable to confirm and carry out and to effectuate fully the
intent and purposes of this Agreement and the transactions contemplated hereby.

                           [SIGNATURE PAGE TO FOLLOW]

                                      -11-
<PAGE>

         IN WITNESS WHEREOF, the parties hereto have caused this Agreement to be
executed by their respective officers or individuals thereunder duly authorized,
as of the date first above written.

PURCHASER:                                       ACACIA RESEARCH CORPORATION


                                                 By:   /S/ PAUL R. RYAN
                                                       -----------------------
                                                       Paul R. Ryan
                                                       Chief Executive Officer

                                      -12-
<PAGE>

            Sellers signature page to Common Stock Purchase Agreement



                                    MILTON ARONOWITZ, JR.

                                    /S/ MILTON ARONOWITZ, JR.
                                    --------------------------------------------

                                    Number of shares of common stock of AMS
                                    held by Seller: 30,000

                                    Number of shares of Acacia Research-
                                    CombiMatrix Common Stock to be received by
                                    Seller: 5,000


                                    PHILIP J. CHELSVIG

                                    /S/ PHILIP J. CHELSVIG
                                    --------------------------------------------

                                    Number of shares of common stock of AMS held
                                    by Seller: 125,000

                                    Number of shares of Acacia Research-
                                    CombiMatrix Common Stock to be received by
                                    Seller: 20,833


                                    DOMINIC F. MORTELLARO


                                    /S/ DOMINIC F. MORTELLARO
                                    --------------------------------------------

                                    Number of shares of common stock of AMS held
                                    by Seller: 50,000

                                    Number of shares of Acacia Research-
                                    CombiMatrix Common Stock to be received by
                                    Seller: 8,333

<PAGE>

                Signature page to Common Stock Purchase Agreement



                                    CARL D. SELKIRK & MARGARET L. SELKIRK

                                    /S/ CARL D. SELKIRK
                                    --------------------------------------------


                                    /S/ MARGARET L. SELKIRK
                                    --------------------------------------------

                                    Number of shares of common stock of AMS held
                                    by Seller: 50,000

                                    Number of shares of Acacia Research-
                                    CombiMatrix Common Stock to be received by
                                    Seller: 8,333


                                    DAVID M. LACKEY

                                    /S/ DAVID M. LACKEY
                                    --------------------------------------------

                                    Number of shares of common stock of AMS held
                                    by Seller: 40,000

                                    Number of shares of Acacia Research-
                                    CombiMatrix Common Stock to be received by
                                    Seller: 6,667


                                    DONALD F. RICHEY, M.D.

                                    /S/ DONALD F. RICHEY, M.D.
                                    --------------------------------------------

                                    Number of shares of common stock of AMS held
                                    by Seller: 25,000

                                    Number of shares of Acacia Research-
                                    CombiMatrix Common Stock to be received by
                                    Seller: 4,167

<PAGE>

                Signature page to Common Stock Purchase Agreement



                                    CALVIN C. LAYLAND DPM INC. PENSION & PROFIT
                                    SHARING PLAN

                                    By:   /S/ CALVIN C. LAYLAND
                                          --------------------------------------
                                          Calvin C. Layland

                                    Number of shares of common stock of AMS held
                                    by Seller: 50,000

                                    Number of shares of Acacia Research-
                                    CombiMatrix Common Stock to be received by
                                    Seller: 8,333


                                    ALAN LYNNE FAMILY LIMITED PARTNERSHIP

                                    By:   /S/ FREDERIC A. GLADLE
                                          --------------------------------------
                                          Frederic A. Gladle, Management Trust
                                          General Partner for the Alan Lynne
                                          Family Limited Partnership

                                    Number of shares of common stock of AMS held
                                    by Seller: 50,000

                                    Number of shares of Acacia Research-
                                    CombiMatrix Common Stock to be received by
                                    Seller: 8,333

<PAGE>

                Signature page to Common Stock Purchase Agreement




                                    DRAKE REVOCABLE TRUST 2001, JOHN D. DRAKE
                                    AND VIRGINIA L. DRAKE, TRUSTEES

                                    By:   /S/ VIRGINIA L. DRAKE
                                          --------------------------------------
                                          Virginia L. Drake, Trustee

                                    Number of shares of common stock of AMS held
                                    by Seller: 250,000

                                    Number of shares of Acacia Research-
                                    CombiMatrix Common Stock to be received by
                                    Seller: 41,667


                                    KEVIN BRUCE KENNELLY

                                    /S/ KEVIN BRUCE KENNELLY
                                    --------------------------------------------

                                    Number of shares of common stock of AMS held
                                    by Seller: 200,000

                                    Number of shares of Acacia Research-
                                    CombiMatrix Common Stock to be received by
                                    Seller: 33,333

<PAGE>

                Signature page to Common Stock Purchase Agreement




                                    FARMER CHILDREN'S TRUST

                                    By:   /S/ IRENE C. FARMER
                                          --------------------------------------
                                          Irene C. Farmer, Trustee

                                    Number of shares of common stock of AMS held
                                    by Seller: 25,000

                                    Number of shares of Acacia Research-
                                    CombiMatrix Common Stock to be received by
                                    Seller: 4,167


                                    PHILIP T. CHING AND/OR BEVERLY S. CHING,
                                    TRUSTEES TO P.T. CHING AND B.S. CHING LIVING
                                    TRUST DTD JUNE 28, 1988

                                    By:   /S/ PHILIP T. CHING
                                          --------------------------------------
                                          Philip T. Ching, Trustee


                                    By:   /S/ BEVERLY S. CHING
                                          --------------------------------------
                                          Beverly S. Ching, Trustee

                                    Number of shares of common stock of AMS held
                                    by Seller: 100,000

                                    Number of shares of Acacia Research-
                                    CombiMatrix Common Stock to be received by
                                    Seller: 16,667

<PAGE>

                Signature page to Common Stock Purchase Agreement




                                    JOSEPH C. TSAI

                                    /S/ JOSEPH C. TSAI
                                    --------------------------------------------

                                    Number of shares of common stock of AMS held
                                    by Seller: 12,000

                                    Number of shares of Acacia Research-
                                    CombiMatrix Common Stock to be received by
                                    Seller: 2,000


                                    CHU LIVING TRUST DATED OCTOBER 2, 2000

                                    By:   /S/ PRISCILLA K. CHU
                                          --------------------------------------
                                          Priscilla K. Chu, Trustee

                                    Number of shares of common stock of AMS held
                                    by Seller: 25,000

                                    Number of shares of Acacia Research-
                                    CombiMatrix Common Stock to be received by
                                    Seller: 4,167


                                    BRIAN T. CHING

                                    /S/ BRIAN T. CHING
                                    --------------------------------------------

                                    Number of shares of common stock of AMS held
                                    by Seller: 40,000

                                    Number of shares of Acacia Research-
                                    CombiMatrix Common Stock to be received by
                                    Seller: 6,667

<PAGE>

                Signature page to Common Stock Purchase Agreement




                                    BRENT D. CHING

                                    /S/ BRENT D. CHING
                                    --------------------------------------------

                                    Number of shares of common stock of AMS held
                                    by Seller: 34,000

                                    Number of shares of Acacia Research-
                                    CombiMatrix Common Stock to be received by
                                    Seller: 5,667


                                    BRADLEY T. CHING

                                    /S/ BRADLEY T. CHING
                                    --------------------------------------------

                                    Number of shares of common stock of AMS held
                                    by Seller: 34,000

                                    Number of shares of Acacia Research-
                                    CombiMatrix Common Stock to be received by
                                    Seller: 5,667


                                    M. ROBERT CHING M.D.
                                    TRUSTEE M. ROBERT CHING
                                    M.D. INC., DEFINED BENEFIT
                                    PENSION PLAN

                                    By:   /S/ M. ROBERT CHING, M.D.
                                          --------------------------------------
                                          M. Robert Ching, M.D., and Trustee

                                    Number of shares of common stock of AMS held
                                    by Seller: 64,500

                                    Number of shares of Acacia Research-
                                    CombiMatrix Common Stock to be received by
                                    Seller: 10,750

<PAGE>

                Signature page to Common Stock Purchase Agreement




                                    M. ROBERT CHING PHYLLIS J. CHING LIVING
                                    TRUST


                                    By:   /S/ M. ROBERT CHING, M. D.
                                          --------------------------------------
                                          M. Robert Ching, M.D., and Trustee

                                    Number of shares of common stock of AMS held
                                    by Seller: 508,000

                                    Number of shares of Acacia Research-
                                    CombiMatrix Common Stock to be received by
                                    Seller: 84,667


                                    FREDERICK L. SIMMONS

                                    /S/ FREDERICK L. SIMMONS
                                    --------------------------------------------

                                    Number of shares of common stock of AMS held
                                    by Seller: 25,000

                                    Number of shares of Acacia Research-
                                    CombiMatrix Common Stock to be received by
                                    Seller: 4,167


                                    PATSY Z. DEWEY

                                    /S/ PATSY Z. DEWEY
                                    --------------------------------------------

                                    Number of shares of common stock of AMS held
                                    by Seller: 25,000

                                    Number of shares of Acacia Research-
                                    CombiMatrix Common Stock to be received by
                                    Seller: 4,167

<PAGE>

                Signature page to Common Stock Purchase Agreement




                                    FRED FINOCCHIARO

                                    /S/ FRED FINOCCHIARO
                                    --------------------------------------------

                                    Number of shares of common stock of AMS held
                                    by Seller: 12,250

                                    Number of shares of Acacia Research-
                                    CombiMatrix Common Stock to be received by
                                    Seller: 2,042