TECHNOLOGY FOCUS - POLYMERS - Preparation (Disclosed): Preparation of the polymer (p1) involves reacting a polymer having a halogenated arylene as a repeating unit with 4-alkoxy-3-(trialkyl stannyl)cyclobut-3-ene-1,2-dione in the presence of transition metal catalysts, followed by treated under an acidic condition, to give the polymer (p1) comprising the compound (I) (where X1 and X2 are O, Z1 is CO and n is 1). Preferred Components: The polyarylene is a compound of formula (II) (preferably poly(aryloxybenzoylphenylene), especially poly(4-phenoxybenzoyl-1,4-phenylene)).R1-R4=substitutional groups or H (preferably benzoyl group or its derivatives);andm= greater than or equal to 6. Preferred Definitions:    X1 and X2=O or S;    Z1=CO;and    n=0-2.    EXAMPLE - To a flask (50 ml) was charged poly(4-phenoxybenzoyl-1,4-phenylene) having isopropyl squarate (0.105 g) and hydrochloric acid (12N, 20 ml). The suspension was stirred at 100 degrees C for 5 hours, and the suspension was filtered and washed with water thoroughly. The hydrolyzed polymer was dried to form a product polymer (Polymer A). After preparing a solution of the Polymer A using N,N-dimethylacetamide, the solvent was removed to obtain a polymer electrolyte Membrane A (test). A stirred solution of poly(4,4'-biphenyleneoxy-4,4'-diphenylsulfone) (1 g) in 1,3-dioxolane (120 ml) was cooled to -78 degrees C and 10 mmol butyllithium (4 ml of a 2.5 M solution) was added dropwise and stirring was continued at -78 degrees C for 60 minutes (solution J). In a separate flask, diisopropyl squarate (2.4 g) was dissolved in 1,3-dioxolane (20 ml), cooled to -78 degrees C and 1.8 mmol of phenyl lithium (1 ml of a 1.8 M dibutylether solution) was added to quench the acidic impurity (solution K). The solution J was cannulated into the solution K. Stirring continued at -78 degrees C for 3 hours and quenched with 2N-hydrochloric acid (5 ml) at -78 degrees C. The solvent ( approximately 3 quarters) was removed under reduced pressure and the remaining solution was added to 2N-hydrochlorc acid (300 ml) to precipitate crude polymer. The polymer was filtered and washed thoroughly with water and dried. The polymer was dissolved in N,N-dimethylformide (20 ml) and poured into 2N-hydrochloric acid to precipitate the purified polymer. The polymer was dried at room temperature to form isopropyl squarate formed polymer (polymer E') (0.90 g). In a round bottomed flask (100 ml), the polymer E'(0.90 g) and concentrated hydrochloric acid (12 N, 20 ml) were stirred at 100 degrees C for 6 hours to hydrolyze isopropoxy group. The polymer was filtered, washed thoroughly with deionized water and dried at ambient temperature to form the polymer bearing squaric acid groups (Polymer E). After preparing a solution of the Polymer E using 1,4-dioxane, the solvent was removed to obtain a Membrane E (comparative). The test/comparative membranes were tested for weight remaining ratio. The test/comparative membranes showed weight remaining ratio of 95.4/72.1%.