Sinteza miktokrakih zvezd vrste A(BC)2 s polimerizacijo z odpiranjem obroča

Šincek, Manca (author), Kranjc, Krištof (mentor), Pahovnik, David (comentor)

Amfifilni blok kopolimeri so blok kopolimeri, ki jih sestavljajo bloki nasprotnih polarnosti. Zaradi te lastnosti, lahko v raztopini oblikujejo različne supramolekularne nanostrukture. Z ureditvijo molekule minimizirajo stik med netopnim blokom in topilom. Vrsta in oblika strukture, ki jo tvorijo, je odvisna od strukturnih lastnosti kopolimera. V magistrskem delu sem razvila sintezni postopek za pripravo amfifilnih blok kopolimerov v obliki trikrake miktokrake zvezde vrste A(BC)2 oziroma A(BA)2. Pri sintezi sem želela doseči natančno definirane dolžine posameznih polimernih blokov. Sintetizirala sem produkte, ki jih sestavljata dva kraka s hidrofobnim blokom poli(propilen oksida) (PPO) in polipept(o)idnega bloka, tretji krak pa sestavlja le polipept(o)idni blok. V primeru A(BA)2 zvezde so vsi trije polipept(o)idni bloki enaki po kemijski sestavi, v primeru A(BC)2 pa se polipept(o)idni blok, vezan direktno na jedro, razlikuje. Ugotovila sem, da sinteza blok kopolimera A(BA)2, v katerem je kot polipeptoidni blok uporabljen polisarkozin, poteka brez težav. Sintetiziramo ga lahko na dva različna načina. Vse tri krake polisarkozina lahko sintetiziramo hkrati, posledično bodo vsi enako dolgi. Z uporabo ortogonalnih zaščitnih skupin pa lahko sintetiziramo tretji krak ločeno in dosežemo drugačno število njegovih ponavljajočih enot. Pri sintezi blok kopolimera C(BA)2, v katerem blok C predstavlja poli(γ-benzil-L-glutamat), sem morala uporabiti pristop z ortogonalnima zaščitnima skupinama, vendar sem naletela na težavo zaradi sterične oviranosti iniciatorske aminske skupine makroiniciatorja, H2N-(BA)2. Dolga polimerna kraka namreč ovirata dostop monomera γ-benzil-L-glutamat N-karboksianhidrida in znatno upočasnjujeta potek polimerizacije. Polimerizacija traja več dni, poleg nje pa poteka tudi stranska reakcija tvorbe homopolimera, kar vodi do nastanka slabo-definiranega produkta. Polimerizacija BLG NCA pri sintezi blok kopolimera A(BC)2, z obratno razporeditvijo polipept(o)idov, poteka hitro, saj iniciatorski aminski skupini makroiniciatorja Boc-(B-NH2)2 nista sterično ovirani.

• Language: Slovenian
• Keywords: polimerizacija z odpiranjem obroča (ROP), epoksidi, N-karboksianhidridi α-aminokislin, amfifilni blok kopolimeri
• Work type: Master's thesis/paper
• Organization: FKKT - Faculty of Chemistry and Chemical Technology
• Year: 2026
• PID: 20.500.12556/RUL-184367
• Publication date in RUL: 06.07.2026

Secondary language

• Language: English
• Title: Synthesis of A(BC)2 miktoarm stars by ring-opening polymerization

Abstract

Amphiphilic block copolymers are block copolymers that consist of blocks of opposite polarity. Due to this property, they can form various supramolecular nanostructures in a solution. By arranging the molecules, they minimize the contact between the insoluble block and the solvent. The type and shape of the structure they form depends on the structural properties of the copolymer. In my master's thesis, I developed a synthesis procedure for the preparation of amphiphilic block copolymers in the form of three-armed miktoarm stars of the A(BC)2 or A(BA)2 type. During the synthesis, I wanted to achieve precisely defined lengths of individual polymer blocks. I synthesized products consisting of two arms with a hydrophobic block of poly(propylene oxide) (PPO) and a polypept(o)ide block, and the third arm consists of only a polypept(o)ide block. In the case of the A(BA)2 star, all three polypept(o)ide blocks are identical in chemical composition, while in the case of A(BC)2, the polypept(o)ide block directly attached to the core differs. I found that the synthesis of the block copolymer A(BA)2, in which polysarcosine is used as the polypeptoide block, does not present any problems. It can be synthesized in two different ways. We can synthesize all three arms of polysarcosine simultaneously, as a result of which they will all be of equal length. However, by using orthogonal protecting groups, we can synthesize the third arm separately and achieve a different number of its repeating units. For the synthesis of the block copolymer C(BA)2, in which the C block is poly(γ-benzyl-L-glutamate), I had to use the approach with orthogonal protecting groups, but I faced a problem due to the steric hindrance of the initiating amine group of the macroinitiator, H2N-(BA)2. Namely, the long polymer arms hinder the access of the monomer γ-benzyl-L-glutamate N-carboxyanhydride and significantly slow down the course of polymerization. The polymerization takes several days, and a side reaction of homopolymer formation also occurs, which results in the formation of a poorly defined product. The polymerization of BLG NCA in the synthesis of the block copolymer A(BC)2, with the arrangement of the polypeptides, proceeds rapidly, since the initiating amine groups of the macroinitiator Boc-(B-NH2)2 are not sterically hindered.

• Keywords: ring-opening polymerization (ROP), epoxides, α-amino acid N-carboxyanhydrides, amphiphilic block copolymers