NOVELTY - Polymers comprising a main chain having both aromatic units and aliphatic units with repeating heteroatoms, and a side chain macromonomer, are new.    USE - In a therapeutic agent containing composition; and in electrolyte containing compositions which are useful in a battery or solar cell (claimed). For opto-electronic applications such as polyelectrolytes in photovoltaic devices as well as in biosensor applications; in dye-sensitized solar cell (DSSC)-devices based on molecular dyes; as candidates for biomedical applications such as biodegradable matrices for tissue engineering; and to deliver therapeutic agents, such as a DNA, proteins, cells or drugs (e.g. to deliver drugs to a target organ or tissue), and to form micelles in aqueous solutions to trap molecules such as drugs, e.g. camptothecin, etoposide, and other anticancer, antibiotic, antiviral, and related drug molecules, in aqueous media.    ADVANTAGE - The polymers have oligomeric poly(ethylene glycol) chains tethered to an irregularly arranged polymer main chain, thus reduces the crystallization of poly(ethylene glycol); provide very high free volume resulting in good segmental mobility while maintaining good mechanical properties, which results in very high ionic conductivity in polymer-ion complexes; and inexpensive and are environmentally stable; are good candidates for opto-electronic applications such as polyelectrolytes in photovoltaic devices as well as in biosensor applications; and have greater stability (thermal and mechanical stability) compared to polymer electrolytes synthesized from starting material having acidic functional groups (e.g. carboxylic acid) and thus used in devices such as batteries and solar cells. The devices fabricated by using the polymers are found to be stable for 10 - 100 hours depending upon the temperature and polymer electrolyte. The polymers can be used in the development of small, lightweight, powerful, safe, environmentally benign, and portable energy sources, such as in batteries or solar cells that are small, light, easy to manufacture, and do not contain toxic compounds. The presence of ester and amide linkages in the polymers as well as their high level of biocompatibility make these polymers good candidates for biomedical applications such as biodegradable matrices for tissue engineering.    DETAILED DESCRIPTION - Polymers of formulae Ra-(C(O)-J(Z1-(CH2)m-Q-C(O)-Z2-CH2-CH2-(Z2-CH2-CH2)n-Z2-CH2-CH2-RZ2)-C(O)-Y-(CH2)v-(Z'-Q-CH2)n1-Y)n2-H (I), or (II) - (VII) containing a main chain having both aromatic units and aliphatic units with repeating heteroatoms, and a side chain macromonomer, are new.    R=H, alkyl, aryl, or arylalkyl;    Ra=OH or alkoxy;    J=(hetero)arylene, or alkylene;    Y=O, S, or NH;    Z', Z1 - Z4=O, S or NH;    Q and Q1=alkylene, alkenylene, alkynylene, or arylene;    m, r=0 - 100;    n, n1=1 - 1000;    n2 and t=1 - 10000;    v=1 - 3;    Rb, R2 - R4=H or alkyl.    INDEPENDENT CLAIMS are included for:    (1) a macromer of formula (Ia);    (2) preparation of a macromonomer comprising:    (a) mixing a monomer or oligomer with an acyl compound to form a monomer mixture;    (b) adding a lipase, an esterase, or a protease to the monomer mixture to form a reaction mixture; and    (c) reacting the reaction mixture, where the macromonomer is an alkylene ester, alkylene amide, or an alkylene thioester;    (3) a polymeric mixture comprising either the compound (II) and (III); or the compound (IV) and (V); or the compound (VI) and (VII);    (4) a composition comprising the polymers and optionally a therapeutic agent;    (5) a composition (C1) comprising the polymers or its reaction product and an electrolyte; and    (6) a battery or solar cell comprising the composition (C1).    R1=H or alkyl.