Tailor-made copolymers are designed based on a peptide-poly(ethylene glycol) (QFFLFFIZPEG) conjugate as a blueprint, to solubilize the photosensitizer meta-tetra-(hydroxyphenyi)chlorin (m-THPC). The relevant functionalities of the parent peptide-PEG are mimicked by employing monomer pairs that copolymerize in a strictly alternating manner. While styrene (5) or 4-vinylbenzyl-phthalimide (VBP) provide aromatic moieties like Phe, the aliphatic isobutyl side chain of Leu4 is mimicked by maleic anhydride (MA) that reacts after polymerization with isobutylamine to give the isobutylamide-carboxyl functional unit (iBuMA). A set of copolymer-PEG solubilizers is synthesized by controlled radical polymerization, systematically altering the length of the functional segment (DPn = 2., 4, 6) and the side chain functionalization (iBuMA, iPrMA, MeMA). The m-THPC hosting and release properties of P[S-alt-iBuMA](6)-PEG reached higher payload capacities and more favored release rates than the parent peptide-PEG conjugate. Interestingly, P[S-alt-RMA](n)-PEG mimics the sensitivity of the peptide-PEG solubilizer well, where the exchange of Leu4 residue by Val and Ala significantly reduces the drug loading by 92%. A similar trend is found with P[S-alt-RMA](n)-PEG as the exchange of iBu -> iPr -> Me reduces the payload capacity up to 78%.