Amphiphilic diblock and ABC triblock methacrylate copolymers: synthesis and aqueous solution characterization Aggeliki I. Triftaridou, Maria Vamvakaki, Costas S. Patrickios * Department of Chemistry, University of Cyprus, P.O. Box 20537, 1678 Nicosia, Cyprus Received 28 October 2001; received in revised form 21 January 2002; accepted 2 February 2002 Abstract Threeisomeric,linear,equimolar,amphiphilicABCtriblockcopolymerscomprisingmethylmethacrylate(MMA,nonionichydrophobic), 2-(dimethylamino)ethyl methacrylate, (DMAEMA, ionizable hydrophilic) and hexa(ethylene glycol) methacrylate (HEGMA, nonionic hydrophilic) units (10 units in each block) were synthesized by group transfer polymerization (GTP). These were the three block sequence isomers,ABC,ACBandBAC.Thecorrespondingrandomterpolymerwasalsoprepared.Themolecularweightsandcompositionsofallthe polymers were characterized by GPC and 1 H NMR. Measurements of the hydrodynamic diameters and cloud points of the copolymers in aqueoussolutionsuggestthatthevariousdistributionsofmonomerunitsinthefourterpolymers(thethreetriblocksandtherandom)resultin different supramolecular structures with different colloidal stabilities. q 2002 Elsevier Science Ltd. All rights reserved. Keywords: ABC triblock copolymers; Block sequence; Amphiphilic polymers 1. Introduction Followingtheintenseinterestinthestudyofdiblockand ABA triblock copolymers [1], the polymer community starts now to focus on a new type of block copolymers, that of ABC triblock copolymers [2] comprising three blocks, each made of a different monomer repeat unit. The presence of three different monomers placed in different blocksconferstothesepolymers,threeratherthantwofunc- tions. Thus, ABC triblock copolymers of suf®ciently high molecular weight (MW) and suf®cient incompatibility between the blocks can form three rather than two micro- phases in the bulk [2]. Although some of these morpholo- gies are direct extensions of the type of microphases encountered in diblock and ABA triblock copolymers, suchastrilamellae[3]andcylindersorspheresatdilamellar interfaces [4], some others are exotic patterns unique to ABC triblock copolymers, such as cylinders surrounded byrings[5]orhelices[6]embeddedinacontinuousmatrix. The solution behavior of ABC triblock copolymers has beenexploredtoamuchsmallerdegreethantheirproperties inthebulk[5,7,8].Alimitednumberofstudiesfocusonthe micellization of these copolymers in solvents, selective for oneortwooftheblocks[9,10].Intheformercase,amicelle with a microphase-separated core was observed [11]. The compositecorewascreatedbythemutualincompatibilityof the two solvent-insoluble blocks. Our own studies involved ABC triblock copolymers in solvents selective for two of theblocks[12±14].Thepresentworkextendsourprevious studieswiththeaimtoexploretheeffectofblocksequence on the behavior of ABC triblock copolymers in water. 2. Experimental section 2.1. Materials and methods The chemical formulas and names of the three monomers, methyl methacrylate (MMA), hexa(ethylene glycol)methacrylate(HEGMA)and2-(dimethylamino)ethyl methacrylate (DMAEMA), and the group transfer poly- merization (GTP) initiator, 1-methoxy-1-trimethylsiloxy- 2-methyl propene (MTS), are shown in Fig. 1. HEGMA is notapurecompound,andthereisadistributionofethylene glycol units in it, with their average number per monomer being between 6 and 7. DMAEMA and MTS were purchased from Aldrich, Germany, while HEGMA was kindly donated by Inspec, UK. All monomers were passed through basic alumina columns to remove the polymeriza- tioninhibitorandproticimpurities.Duetothehighviscosity oftheneatmonomer,a50%v/vsolutioninfreshlydistilled tetrahydrofuran (THF) of the HEGMA monomer was used for processing with basic alumina. The HEGMA monomer Polymer 43 (2002) 2921±2926 0032-3861/02/$ - see front matter q 2002 Elsevier Science Ltd. All rights reserved. PII:S0032-3861(02)00115-5 www.elsevier.com/locate/polymer * Corresponding author. E-mail address: costasp@ucy.ac.cy (C.S. Patrickios).