Conformation of Cylindrical Brushes in Solution:  Effect of Side Chain Length

Zhang, Bin; Gröhn, Franziska; Pedersen, Jan Skov; Fischer, Karl; Schmidt, M

doi:10.1021/ma0613178

Cited by 187 publications

(319 citation statements)

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“…Such polymers are widely termed 2 "cylindrical molecular brushes" due to their steric-induced stiffness and axes of symmetry. [39][40][41][42][43] These cylindrical brushes can be modeled as wormlike chains with the same average crosssectional radius (Rc) along the entire backbone. 5,[44][45][46] On the other hand, if the macromonomer and diluent copolymerize at different rates, the resulting gradient sequences are anticipated to template different side chain conformations.…”

Section: Introductionmentioning

confidence: 99%

Design, Synthesis, and Self-Assembly of Polymers with Tailored Graft Distributions

et al. 2017

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Grafting density and graft distribution impact the chain dimensions and physical properties of polymers. However, achieving precise control over these structural parameters presents long-standing synthetic challenges. In this report, we introduce a versatile strategy to synthesize polymers with tailored architectures via grafting-through ring-opening metathesis polymerization (ROMP). One-pot copolymerization of an ω-norbornenyl macromonomer and a discrete norbornenyl co-monomer (diluent) provides opportunities to control the backbone sequence and therefore the side chain distribution. Toward sequence control, the homopolymerization kinetics of 23 diluents were studied, representing diverse variations in the stereochemistry, anchor groups, and substituents. These modifications tuned the homopolymerization rate constants over two orders of magnitude (0.36 M −1 s −1 < khomo < 82 M −1 s −1 ). Rate trends were identified and elucidated by complementary mechanistic and density functional theory (DFT) studies. Building on this foundation, complex architectures were achieved through copolymerizations of selected diluents with a poly(D,L-lactide) (PLA), polydimethylsiloxane (PDMS), or polystyrene (PS) macromonomer. The cross-propagation rate constants were obtained by non-linear least squares fitting of the instantaneous co-monomer concentrations according to the Mayo-Lewis terminal model. Indepth kinetic analyses indicate a wide range of accessible macromonomer/diluent reactivity ratios (0.08 < r1/r2 < 20), corresponding to blocky, gradient, or random backbone sequences. We further demonstrated the versatility of this copolymerization approach by synthesizing AB graft diblock polymers with tapered, uniform, and inverse-tapered molecular "shapes." Small-angle X-ray scattering analysis of the self-assembled structures illustrates effects of the graft distribution on the domain spacing and backbone conformation. Collectively, the insights provided herein into the ROMP mechanism, monomer design, and homo-and copolymerization rate trends offer a general strategy for the design and synthesis of graft polymers with arbitrary architectures. Controlled copolymerization therefore expands the parameter space for molecular and materials design.

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Section: Introductionmentioning

confidence: 99%

Design, Synthesis, and Self-Assembly of Polymers with Tailored Graft Distributions

et al. 2017

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“…3 Recent SANS investigations on the conformation of polystyrene-grafted polymethacrylate show a flexible coil to stiff cylinder transition as the length of the side chains increases. 5 OEG-grafted polymers are promising materials for different applications owing to the special properties of EG in addition to the comblike architecture, which allows independent variation of the length and composition of the backbone and side chains to achieve desired structures and functions. A main research activity involves optimization of the properties of OEG-grafted polymers as polymer electrolytes where the OEG side chains are good ionic conductors.…”

Section: Introductionmentioning

confidence: 99%

Small Angle Neutron Scattering Study of Conformation of Oligo(ethylene glycol)-Grafted Polystyrene in Dilute Solutions: Effect of the Backbone Length

et al. 2008

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The conformation and clusterization of comblike polymers of polystyrene densely grafted with oligo(ethylene glycol) (OEG) side chains in 1.0 wt % solutions of D 2 O, toluene-d 8 , and methanol-d 4 was investigated as a function of the degree of polymerization (DP) of the backbone by small angle neutron scattering (SANS). Each side chain had four EG repeat units, and the DP of the polystyrene backbone varied from 8 to 85. The global conformation of the polymers in toluene and methanol was shown to assume ellipsoidal, rigid cylindrical, or wormlike morphologies with increasing DP of the polystyrene backbone. At the same time, in D 2 O, the polymer conformation was described by the form factor of rigid cylinders. The second viral coefficient A 2 was measured for the polymer with a DP of 85 in all three solvents, and the solvent quality of toluene, methanol, and D 2 O was identified to be good, marginal, and poor, respectively, for this polymer. Because of a poor solvent quality, the PS backbone (DP ) 85) is partially collapsed in D 2 O, whereas it is moderately expanded in toluene and methanol. Polymers with a DP of 8 were found to form clusters in all three solvents, with the characteristic size between 100 and 200 Å and a fractal dimension of 2. With the increase in the DP, the clusters diminished in D 2 O and completely disappeared in toluene and methanol. This observation suggests that the clusterization of these short side-chain polymers is caused by end-group and hydrogen bonding interactions between different chains.

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“…These results are similar to those observed for PS-MA PM in toluene and cyclohexane. 17,19 The unperturbed mean-square radius of gyration, /S 2 S 0 , for wormlike chains with a contour length L is expressed as 20…”

Section: Resultsmentioning

confidence: 99%

“…[10][11][12] We have studied PM consisting of a PS main chain and PS side chains with a benzyl group at each end (benzyl-PS PM) and showed that its A 2 in cyclohexane vanishes at 34.5 1C, which is identical to the Y temperature of linear PS in cyclohexane. [13][14][15][16] In contrast, the values of A 2 for PM consisting of a polymethacrylate main chain and PS side chains with a butyl group at each end (PS-MA PM) in d 12 -cyclohexane were shown to be positive at 20 1C, 17 far below the Y temperature (40 1C) of linear PS in d 12 -cyclohexane. Although the butyl end in PS-MA PM may be a primary cause of the positive A 2 , there may be a possible effect on the A 2 of the polymethacrylate main chain.…”

Section: Introductionmentioning

confidence: 88%

“…This differs from the known behavior of linear PS and benzyl-PS PM in the same solvent in that A 2 decreases with decreasing T and becomes zero at 34.5 1C, [13][14][15][16] but the results are similar to those observed for PS-MA PM. 17,19 The molecular weight dependence of A 2 for butyl-PS PM is illustrated in Figure 4, in which the filled and unfilled circles represent the data points for the toluene and cyclohexane solutions, respectively. The data points for the cyclohexane solutions are systematically lower than those for the toluene solutions, showing that the former solvent is poorer than the latter solvent.…”

Section: Scattering Functionmentioning

confidence: 99%

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Effects of side-chain ends on the stiffness and excluded-volume parameters of polymacromonomers

Kanda

Nakamura

2011

Polym J

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Light and small-angle X-ray scattering measurements were taken on cyclohexane and toluene solutions of a polystyrene (PS) polymacromonomer (PM) having side chains consisting of 19 styrene residues and an n-butyl group (butyl-PS PM) at each end. The second virial coefficient, A 2 , of the butyl-PS PM in cyclohexane was positive in the temperature range of 15.0-34.5 1C, differing from previous results for PS PMs with benzyl ends (benzyl-PS PM) whose A 2 vanished at 34.5 1C. The mean-square radius of gyration, /S 2 S, for the butyl-PS PM in cyclohexane at 34.5 1C was much larger than that for the benzyl-PS PM with the same side-chain length, indicating large effects of the side-chain ends on intramolecular interactions, whereas the difference in /S 2 S between these polymers in toluene at 15.0 1C was quite small. From these data, the stiffness parameter and the excluded-volume strength were determined with the aid of theories for the wormlike chain model. The effects of the side-chain ends on these parameters are discussed according to recently developed theories. Polymer Journal (2012) 44, 252-256; doi:10.1038/pj.2011.132; published online 14 December 2011Keywords: branched polymer; light scattering; polymacromonomer; polystyrene; small-angle X-ray scattering; solution properties INTRODUCTIONThe second virial coefficient, A 2 , of linear polystyrene (PS) with a butyl end in cyclohexane at the Y temperature (34.5 1C) was known to increase with decreasing molecular weight, M, when M is lower than 10 4 , which had been considered to be the effects of the threesegment interactions. 1 Yamakawa 2 interpreted this increase as an effect of chain ends in 1992. Since then, studies were undertaken to address the chain-end effect on A 2 for several kinds of polymers. 3-9 Among them, PS solutions were the most precisely examined. Because the chain-end effect on A 2 of linear PS with a benzyl end, in contrast to a butyl end, was negligibly small, 7 the increase in A 2 of PS at low M was ascribed to the effects of the butyl end. Recently, a similar study was carried out on the A 2 of a four-arm star PS with a butyl group at each arm end and showed that the increase in A 2 at Y with decreasing M begins at a higher value of M than that for linear PS with the same end group. 8 This study indicates that the chain-end effect becomes more significant with an increasing number of branches. Therefore, one may expect the chain-end effect to be much larger for comb polymers that have many more branches.Polymacromonomer (PM), a type of comb-branched polymer with dense side chains, is known to behave as a stiff chain in solution because of the interactions between its side chains. [10][11][12] We have studied PM consisting of a PS main chain and PS side chains with a benzyl group at each end (benzyl-PS PM) and showed that its A 2 in cyclohexane vanishes at 34.5 1C, which is identical to the Y temperature of linear PS in cyclohexane. [13][14][15][16] In contrast, the values of A 2 for PM consisting of a polymethacrylate main chain and PS sid...

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Conformation of Cylindrical Brushes in Solution: Effect of Side Chain Length

Cited by 187 publications

References 59 publications

Design, Synthesis, and Self-Assembly of Polymers with Tailored Graft Distributions

Design, Synthesis, and Self-Assembly of Polymers with Tailored Graft Distributions

Small Angle Neutron Scattering Study of Conformation of Oligo(ethylene glycol)-Grafted Polystyrene in Dilute Solutions: Effect of the Backbone Length

Effects of side-chain ends on the stiffness and excluded-volume parameters of polymacromonomers

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