Determining the Polydispersity in Chemical Composition and Monomer Sequence Distribution in Random Copolymers Prepared by Postpolymerization Modification of Homopolymers

Abstract

We report on establishing the polydispersity in chemical composition (PCC) and polydispersity in monomer sequence distribution (PMSD) in random copolymers of poly(styrene-co-4-bromostyrene) (PBr x S), where x = (0.385 ± 0.035) is the mole fraction of the 4bromostyrene units (4-BrS), prepared by electrophilic substitution of bromine in the para-position of the phenyl ring of the parent polystyrene. Upon fixing the total number of repeating units, we tune the distribution of styrene and 4-BrS segments in PBr x S by carrying out the bromination reaction on polystyrene homopolymers in different solvents. While PBr x S with relatively random comonomer distribution is prepared in 1-chlorodecane, random-blocky sequences of 4-BrS in PBr x S are achieved by carrying out the bromination reaction in 1-chlorododecane. The PCC in both copolymers is established by fractionating both polymers using interaction chromatography (IC) and determining the chemical composition of the individual fractions by neutron activation analysis (NAA). The NAA data along with IC experiments reveal that the random-blocky sample possesses a narrowed PCC relative to a specimen with a more random comonomer sequence distribution. The full width at halfmaximum (fwhm) in the chemical composition profile from IC is used to quantify PCC; the random mother sample possessed a 25% fwhm, while the random blocky mother sample has a fwhm equal to 8.7%. The change in the adsorption enthalpy per brominated segment due to adsorption is determined to be ≈1.5 times greater for the random-blocky than the relatively random sample, proving that more pronounced cooperative adsorption occurs in the case of the random-blocky sample relative to the random copolymer sample. Computer simulation employing the discontinuous molecular dynamic scheme further reveals that the distribution of comonomer sequences, that is, PMSD, in the random-blocky copolymer is narrower than that in the copolymer with a random distribution of both monomers.

Linear Gradient Quality of ATRP Copolymers

“…Several experimental ,− and kinetic modeling studies ,− were reported in which the influence of copolymerization conditions on the monomer sequence and, hence, the copolymer properties was investigated in CRP processes. It was shown that copolymer composition drift can exist under both homogeneous and heterogeneous ATRP batch conditions, ,, and a semibatch approach can be beneficial. ,,, For example, simulations based on the method of moments and the kinetic Monte Carlo (kMC) technique showed that semibatch ATRP allows to optimize the comonomer feed rates to achieve a desired overall copolymer composition. , However, in these modeling studies the copolymer composition was not explicitly tracked.…”

Precise Compositional Control and Systematic Preparation of Multimonomeric Statistical Copolymers

“…There is a growing interest in the polymer science landscape to access architecturally tailored and sequence-specified macromolecules to acquire enhanced properties. Structurally controlled polymers are of widespread importance across many diverse fields, from drug delivery to photovoltaics and microlithography .…”

Bench-Scale Synthesis and Characterization of Biodegradable Aliphatic–Aromatic Random Copolymers with 1,4-Cyclohexanedimethanol Units Toward Sustainable Packaging Applications

“…The sequence distribution of the PBCCTs was also analyzed using 13 C NMR spectroscopy, as shown in Figures S2 and S3, to determine the microstructure of the backbone, such as the degree of randomness and number-average sequence length. , As shown in Table S1, the molar fractions ( f ) of each dyad were obtained by integrating the relative peak areas. The number-average sequence length ( L ) and the degree of randomness ( R ) of these dyads were calculated based on the amounts of carbonate and terephthalate according to previously published equations. , The microstructure of the resulting polymers, i.e., whether they are random, block-like, or alternating structures, influences the materials properties significantly. , As such, the degrees of randomness based on carbonate ( R C* ) were calculated and found to be 1.09 (PBCCT10), 0.92 (PBCCT20), 0.96 (PBCCT30), 0.96 (PBCCT40), and 0.98 (PBCCT50), and the degrees of randomness values based on terephthalate ( R T ) were 1.16 (PBCCT10), 1.01 (PBCCT20), 0.99 (PBCCT30), 0.98 (PBCCT40), and 0.95 (PBCCT50). In the case of a random copolymer, R takes a value of 1, while alternate copolymer and block copolymer take values of 2 and near 0, respectively. , Therefore, the R values of all the synthesized PBCCTs close to 1 suggests that they were random copolymers with a uniformly distributed sequence of monomers.…”

“…39,40 The microstructure of the resulting polymers, i.e., whether they are random, block-like, or alternating structures, influences the materials properties significantly. 41,42 As such, the degrees of randomness based on carbonate (R C* ) were calculated and found to be 1.09 (PBCCT10), 0.92 (PBCCT20), 0.96 (PBCCT30), 0.96 (PBCCT40), and 0.98 (PBCCT50), and the degrees of randomness values based on terephthalate (R T ) were 1.16 (PBCCT10), 1.01 (PBCCT20), 0.99 (PBCCT30), 0.98 (PBCCT40), and 0.95 (PBCCT50). In the case of a random copolymer, R takes a value of 1, while alternate copolymer and block copolymer take values of 2 and near 0, respectively.…”