SYNTHESES AND MALDI-TOF MS CHARACTERIZATION OF TAILORED POLY(4-VINYL PIRIDINE) BASED COPOLYMERS

A series of poly(4-vinylpyridine) based copolymers such as poly(styrene-co-4-vinylpyridine) [P(S-4VP)] random copolymers and P[CPDTBT-block-(S-4VP)] rod-coil block copolymers (CPDTBT notes the 4,4-bis-(2-ethylhexyl)-4H-cyclopenta[2,1-b:3.4-b']dithiophene)-alt-4,7-(2,1,3-benzothiadiazole units) were appropriately synthesized through nitroxide-mediated controlled-radical polymerization (NMRP) using (2,2,5-Trimethyl-4-phenyl-3-azahexane-3-nitroxide) (TIPNO) as a mediator.[1,2] Their molar composition was estimated by 1H-NMR and in particular by MALDI-TOF MS analysis. MALDI-TOF MS analysis of both series of copolymers reveals the presence of intact "dormant" copolymer chains terminated with TIPNO at one end. Moreover, in the case of the P(CPDTBT-block-(S-4VP)) rod-coil block copolymers the MALDI-TOF MS analysis reveals that high purity rod-coil block-copolymers were obtained applying a severe purification procedure constituted by repeated precipitations with selective solvents. The chemical composition of the P(S-4VP) copolymers was evaluated by means of the MACO/MALDI-TOF MS analysis. This analytical method allows to extract detailed information on the composition of the copolymer samples and their structure. The MACO statistical model applied to the higher mass resolved mass spectra recorded in reflectron mode, allows to extract detailed information on the composition of the copolymer samples and their structure. Our work shows that the MACO/MALDI-TOF MS analysis can be successfully applied to copolymers having a difference between the mass of the comonomers as small as 1 g mol-1 as well the styrene and 4-vinylpyridine units: 104.15 and 105.15 g/mol, respectively, which results in overlapping isotopic patterns.[1] For each mass peak the MACO program evaluates the different number of combination of comonomers along the copolymers chains with the same end groups, taking into account of the natural abundances of the isotope of the various atom components. Therefore a pertinent and correct assignment can be carried out. A section of the mass spectrum of P(S-4VP) copolymer and its calculated mass peak distributions is highlighted in Figure 1.