Zwitterionic Poly(vinylidene fluoride) Graft Copolymer with

Subscriber access provided by UNIV OF WESTERN ONTARIO

Interface Components: Nanoparticles, Colloids, Emulsions, Surfactants, Proteins, Polymers

Zwitterionic Poly(vinylidene fluoride) Graft Copolymer with Unexpected Fluorescence Property MAHUYA PAKHIRA, Radhakanta Ghosh, Santi Prasad Rath, Dhruba P Chatterjee, and Arun Kumar Nandi Langmuir, Just Accepted Manuscript • DOI: 10.1021/acs.langmuir.9b00039 • Publication Date (Web): 20 Mar 2019 Downloaded from http://pubs.acs.org on March 20, 2019

Just Accepted “Just Accepted” manuscripts have been peer-reviewed and accepted for publication. They are posted online prior to technical editing, formatting for publication and author proofing. The American Chemical Society provides “Just Accepted” as a service to the research community to expedite the dissemination of scientific material as soon as possible after acceptance. “Just Accepted” manuscripts appear in full in PDF format accompanied by an HTML abstract. “Just Accepted” manuscripts have been fully peer reviewed, but should not be considered the official version of record. They are citable by the Digital Object Identifier (DOI®). “Just Accepted” is an optional service offered to authors. Therefore, the “Just Accepted” Web site may not include all articles that will be published in the journal. After a manuscript is technically edited and formatted, it will be removed from the “Just Accepted” Web site and published as an ASAP article. Note that technical editing may introduce minor changes to the manuscript text and/or graphics which could affect content, and all legal disclaimers and ethical guidelines that apply to the journal pertain. ACS cannot be held responsible for errors or consequences arising from the use of information contained in these “Just Accepted” manuscripts.

is published by the American Chemical Society. 1155 Sixteenth Street N.W., Washington, DC 20036 Published by American Chemical Society. Copyright © American Chemical Society. However, no copyright claim is made to original U.S. Government works, or works produced by employees of any Commonwealth realm Crown government in the course of their duties.

Page 1 of 27 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Langmuir

Zwitterionic Poly(vinylidene fluoride) Graft Copolymer with Unexpected Fluorescence Property Mahuya Pakhiraa, Radhakanta Ghosha, Santi P. Rathb Dhruba P. Chatterjeec and Arun K. Nandi* Polymer Science Unit, School of Materials Science, Indian Association for the cultivation of Science, Jadavpur, Kolkata-700 032, INDIA Abstract: Recently there is a growth of research on non-conjugated polymer exhibiting fluorescence property and it would be exciting if fluorescence property is developed in zwitterionic polymers because of their good water solubility. Poly(vinylidene fluoride) (PVDF) grafted with poly(dimethyl amino ethyl methacrylate) (PDMAEMA) is fractionated and a highly water soluble fraction (PVDM-1) is quaternized with 1,3 propane sultone, producing a zwitterionic polymer, PVDF-g-PDMAEMA-sultone (PVDMS). PVDM-1 shows fluorescence property with a very low quantum yield (1%) in water, but on quaternization the fluorescence quantum yield increases to 8%. Transmission electron microscopy (TEM) results indicate that the PVDM-1 cast from water has vesicular morphology whereas PVDMS exhibits aggregated vesicular morphology. The 1H NMR spectra indicate the presence of

a Polymer

b School

Science Unit, IACS

of Chemical Sciences, IACS

c Department

of Chemistry, Presidency University, Kolkata -73

*For correspondence: A. K. Nandi, Email: [email protected] 1 ACS Paragon Plus Environment

Langmuir 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

72 mol% DMAEMA in PVDM-1 whose 66% of -NMe2 groups are quaternized upon post polymerization modification. PVDM-1 exhibits absorption peaks at 210, 276 and 457 nm with a hump at 430 nm whereas PVDMS exhibits two absorption peaks at 203 and 297 nm. PVDM-1 exhibits a broad emission peak at 534 nm whereas PVDMS exhibit a sharp emission peak at 438 nm. Attempt has been made from density functional theory (DFT) calculations to shed light on the origin of fluorescence in both PVDM-1 and in the zwitterionic PVDMS. The excitonic decay occurs from LUMO of carbonyl group to HOMO of tertiary amine group for PVDM-1 whereas in PVDMS the excitionic transition occurs from LUMO situated over the quaternary ammonium group, to the HOMO located on the electron rich terminal sulphonate group. Introduction: Poly (vinylidene fluoride) (PVDF) is a technologically important polymer because of its good membrane forming property1 and also for its electronic (piezo and pyroelectric)2 properties. However due to its hydrophobic nature it has difficulty for its application in different fields, particularly in biomedical application, when modification of the pristine PVDF is necessary.3 In this regard, grafting with different polymeric chain is a useful way retaining the mechanical properties of polymer.4 In this respect both hydrophobic and hydrophilic polymers are grafted, the former improves its solubility in organic solvents whereas the later makes it soluble in aqueous medium.3 Some ionic character is also introduced by postmodification of the grafted chains.5,6 This kind of polyelectrolyte with precisely controlled macromolecular architecture and self-assembled nature have received significant attention in the area of molecular recognition, surface modification and various biological application because of their unique binding properties and ability to interact with chemo/bio-molecules.7 In literature there are some reports of cationic or anionic polyelectrolyte based surface 2 ACS Paragon Plus Environment

Page 2 of 27

Page 3 of 27 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Langmuir

modifications of pristine PVDF.8,9 The zwitterionic polymers exhibit interesting properties1013 and

in this manuscript we report the synthesis and properties of the zwitterionic PVDF graft

copolymer with unexpected strong blue emission property. To stimulate the usefulness of graft copolymers in different appliances the optical property of the polymer is very important and useful. Usually conjugated polymer exhibit fluorescence property which can be tuned by grafting with stimuli responsive polymers followed by varying the stimulants.14 It is now an interesting topic of research that polymers without having any aromatic chromophore moiety possesses fluorescence property.15-19 Polymers with auxochromophores, tertiary amines, amide, ester etc are now found to exhibit fluorescence property which mainly arises due to clustering of functional groups emitting the fluorescence. Recently polymer dots of non-conjugated polymers are also reported to exhibit fluorescence property similar to that of carbon dots.20,21 PL emission arises due to the clustering of the locked carbonyl groups.22 The fluorescence property of the unconjugated fluorophores, usually termed as subfluorophores, are found to be low and can be enhanced by immobilizing the polymer chain containing it.23 The mechanism of emission in these polymers containing subfluorophore is yet obscure. Different reasons e.g. oxidation of amino group attached to the polymer24, interaction between phenyl group with the carbonyl group,22 aggregation of multiple >C=O group of polymers25, and most recently the n-π* interaction of electron lone pair of –OH group and π* orbital of >C=O units19 are proposed by different research groups. The fluorescent polymers, without aromatic ring in the chain, may have good potential for application in sensing, drug delivery, gene delivery, biotechnology etc. 22,26,27 So it is really beneficial to synthesize new fluorescent polymers from the technologically important commercial polymer poly(vinylidene fluoride) (PVDF). In the present report we have grafted 3 ACS Paragon Plus Environment

Langmuir 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

poly(dimethyl amino ethyl methacrylate) (PDMAEMA) from PVDF backbone. This PVDFg-PDMAEMA was fractionated to get the highly soluble fraction (PVDM-1) for optical clarity and it shows small vesicular morphology and fluorescence property with a low quantum yield (1%) in water. Here PVDF plays a crucial role in guiding the self-assembly into vesicles through hydrophobic and hydrophilic balance and aggregation induced emission occurs from the non-fluorescent chromophores. We have then quaternized it with propane sultone, thus producing a zwitterionic polymer, PVDF-g-PDMAEMA-Sultone (PVDMS), that exhibits aggregated vesicular morphology increasing the fluorescence quantum yield to 8%. After zwitterion formation the aggregation is more, facilitating sharp enhancement of the fluorescence property. An application of the interesting zwitterionic polymer has been made to detect the ionic surfactants in water. Attempt has been made to understand the origin of fluorescence property using density functional theory (DFT). To our knowledge, it is a first report to show that PVDF derivative without a fluorophore exhibits a strong fluorescence property.

Experimental: Materials: Poly(vinylidene fluoride) (PVDF, Aldrich, Mn= 7.1× 104, PDI = 2.57, head to head (H-H) defect = 4.33 mol %) was recrystallized from its 0.2% (w/w) acetophenone solution. 2(dimethyl amino)ethyl methacrylate (DMAEMA, 98%, Sigma-Aldrich) was treated with basic alumina to remove inhibitor. 4,4‫–׳‬Dimethyl-2,2‫׳‬-Dipyridyl (DMDP, 99.5%, SigmaAldrich) and 1,3 propane sultone (Sigma-Aldrich) were used as received. CuCl (Aldrich) was purified by a reported procedure.5 The solvents N-Methyl-2-pyrrolidone (NMP), THF, methanol (RANKEM, RFCL limited New Delhi) were distilled before use and Milli Q water was used throughout the work for making different aqueous solutions. Sodium dodecyl 4 ACS Paragon Plus Environment

Page 4 of 27

Page 5 of 27 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Langmuir

benzene sulfonate (SDBS, Sigma-Aldrich), cetyltrimethylammonium bromide (CTAB, Sigma-Aldrich) and polyethylene glycol 4-tert-octylphenolether (Triton X-100, SRL) were used as received. Synthesis

of

poly(vinylidinefluoride)-g-poly(2-dimethylaminoethyl

methacrylate)

(PVDF-g-PDMAEMA, PVDM): In a N2 purged reaction vessel (8 × 2.5), PVDF (0.1 g) was dissolved in 1ml NMP. Then the ligand, DMDP (0.44 g, 0.24 mmol), and catalyst, CuCl (0.01 g, 0.1 mmol), were added to it. The monomer, DMAEMA (0.5 ml, 2.95 mmol), was lastly injected into the vessel and was sealed with rubber septum. The reaction mixture was placed in a preheated reaction bath at 90 ºC. After 24 h of reaction, the mixture was diluted with 1 ml NMP and was precipitated into excess petroleum ether. The precipitated polymer was isolated, re-dissolved in NMP and reprecipitated in petroleum ether. This process was repeated three times to remove any unreacted monomer. Then the dried polymer was repeatedly washed with double distilled water to remove residual copper catalyst. Finally pure graft copolymer was obtained by drying in vacuum at 50 °C. It was then separated via fractionation as the prepared graft copolymer was difficultly soluble in water. The fractionation was carried out using soxhlation with THF for 48 h and thereby extracting the high PDMAEMA content PVDF which was easily soluble in water. The first fraction of the graft copolymer so obtained is named PVDM1 and before fractionation the graft copolymer is named as PVDM. Post-polymerisation modification of PVDM-1 with 1, 3-propane sultone: PVDM-1 was modified via the quaternization reaction with 1, 3-propane sultone. In a 100 ml round-bottom flask 300 mg of PVDM-1 was dissolved in 20 ml methanol. An excess amount (0.5g) of 1, 3-propane sultone was added to it. The progress of the reaction was easily monitored by the appearance of insoluble residue in the flask after 5-6 h. The reaction was 5 ACS Paragon Plus Environment

Langmuir 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

continued overnight with continuous stirring at 30 ºC to achieve maximum conversation. Then the white insoluble residue was filtered, washed with methanol repeatedly and was finally dried under vacuum at 40 ºC for 2 days producing the zwitterionic derivative of PVDF (PVDMS). Instrumentation: Nuclear Magnetic Resonance (NMR): The 1H NMR spectra of PVDF graft copolymer (before and after fractionation) and PVDMS were recorded on a Bruker 500 MHz NMR spectrometer using DMSO-d6 and D2O as the solvent respectively. Advanced Polymer Chromatography (APC): The molecular weight of graft polymers were measured by APC using PMMA as a standard. APC was executed on a Water Acquity Advanced Polymer Chromatography equipped with two Acquity APC columns (XT450, XT200). DMF was used as eluent at a flow rate of 0.5ml per min at 25 ºC. Fourier transform infrared spectroscopy (FT-IR): FT-IR spectra of solid samples of PVDF, PVDM-1 and PVDMS were performed on Perkin-Elmer (Spectrum -2). Transmission electron microscopy (TEM): The morphology of polymer samples were captured in HRTEM instrument (JEOL, 2010EX) operated at 200 kV acceleration voltage. Polymer films were cast from their respective aqueous solutions on carbon coated copper grid. UV-vis and Photoluminescence (PL) Spectroscopy: UV-vis spectra of aqueous solution of PVDM-1 and PVDMS were recorded in a UV-vis spectrophotometer (Agilent, Cary 8454) using a quartz cell (10 mm path length) from 190 to 1100 nm. Fluorescence emission spectra were examined in Fluoromax-3 instrument (Horiba Jobin Yvon) using a quartz cell of 10 mm path length and slit width of 5 mm for both excitation and emission. The PL quantum yield of PVDM-1 and PVDMS were measured using Quinine Sulphate in 0.1M H2SO4 (QY= 0.58 at

6 ACS Paragon Plus Environment

Page 6 of 27

Page 7 of 27 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Langmuir

350 nm) as a standard.27 Fluorescence quantum yield were estimated by this known reference quantum yield value and using the following equation------------ (1) Where A is absorbance at excitation wavelength, η is the refractive index of solvent, I is the integrated area under the fluorescence emission curve at the same excitation wavelength. 27 X-ray photoelectron spectrometry (XPS): XPS spectrum of PVDMS (cast from aqueous medium) was performed with an Omicron Nano Technology (model 0571) XPS spectrometer, using the monochromated A1 Kα X-ray source (1486.8 eV). Computational study: All theoretical calculations were performed using Gaussian 0928 suit of a program. B3LYP/631+G29 (for C, H, N, O atoms) and 6-311+G30 (for S atom) level of theory were employed for all structural optimization and vibrational analysis. The calculations of the ground singlet states were performed using either spin-restricted or spin-unrestricted approaches. Gaussian fragmentation job was setting up to imply the corresponding charges on N and S atoms in PVDMS. Singlet excitation energies based on the solvent-phase (water) optimized geometry of the complexes were computed using the time-dependent density functional theory (TDDFT)31,32 formalism in water using the conductor-like polarizable continuum model (CPCM)33-36. Results and Discussion: Synthesis and Characterization: In the present work, synthesis of PVDF based zwitterionic graft copolymer is carried out by a two-step methodology (Scheme-1), where in the first step controlled grafting of PDMAEMA chains on PVDF backbone is carried out following our previously developed protocol5 using copper based atom transfer radical polymerization (ATRP) of DMAEMA and then post


Langmuir 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 8 of 27

Scheme-1. Synthesis of PVDF based zwitterionic graft copolymer (PVDMS).

PVDM-1 NMP

PVDF

PVDMS

polymerization modification of the graft copolymer through quaternization with 1, 3-propane sultone. Fig 1(a) presents the 1H-NMR spectrum of the as synthesized PVDM graft copolymer in DMSO-d6 along with the characteristic proton of PVDF and PDMAEMA segments. Signal ‘xʹ’, ‘y′’, and ‘z′’ arises at 3.99, 2.5, 2.2 ppm respectively3,5 corresponding

(a)

(b)

(c)

Figure 1. 1HNMR spectra of (a) PVDM, (b) PVDM-1 in DMSO-d6 and (c) PVDMS in D2O along with their peak assignments. 8 ACS Paragon Plus Environment

Page 9 of 27 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Langmuir

to alkoxymethylene group (-OCH2CH2NMe2) of PDMAEMA unit. The >CH2 protons (‘d’) of (H-T) unit of PVDF arises at 2.89 ppm.5 Signals corresponding to ‘xʹ’ and ‘d’ protons are used for calculation of mole ratio of VDF and DMAEMA in the synthesized graft copolymer (PVDM). The analysis shows 22 mole% of DMAEMA units are present in the as prepared graft copolymer. The total molecular weight of the graft copolymer is also calculated following the given equation------------ (2) Here ‘j’ is the molar ratio of DMAEMA units present in the graft copolymer as obtained from signal area ratio of signals ‘x′’ and ‘d’. M0DMAEMA is the molar mass of the DMAEMA monomer units and M0PVDF is the molar mass of PVDF repeating unit37 and the supplied value of Mn,PVDF = 71,000. This results in the molecular weight of the PVDM graft copolymer (Mn,) to be 115800. The synthesized graft copolymer subsequently fractionated by soxhlation in water to extract the freely water soluble portion of it which is named as PVDM-1. The 1HNMR spectrum of PVDM-1 in DMSO-d6 is given in Figure 1(b) which shows significant rise in relative intensity of DMAEMA signals with respect to the PVDF (H-T, >CH2) signal. This indicates successful fractionation of the graft copolymer as largely water insoluble PVDF rich grafted chains are eliminated. The SEC analysis of the graft copolymer before and after fractionation is given in Figure S1 which shows a significant shift of the SEC trace towards higher elution volume after fractionation. This indicates that molecular weight of the water soluble PVDM-1 should be lower than the synthesized graft copolymer PVDM. However, calculation of the SEC molecular weight is of less significance here as linear poly(methyl methacrylate) standards are used for column calibration. The analysis of 1H-NMR spectrum in Figure 1(b) also indicates that a much increased molar proportion (72 mole %) of 9 ACS Paragon Plus Environment

Langmuir 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 10 of 27

DMAEMA units with respect to VDF units is present in PVDM-1 accounting for its very good aqueous solubility. Condensation of 1, 3-propane sultone is carried out then with the pendant (-NMe2) groups of grafted PDMAEMA chains of PVDM to obtain the desired zwitterionic graft copolymer which is named PVDMS. This zwitterionic graft copolymer is no longer soluble in DMSO but is highly soluble in water. Figure 1(c) shows the 1H-NMR spectrum of PVDMS in D2O along with the assignment of different protons. Expectedly in this spectrum, the signals corresponding to the PVDF methylene protons are absent due to their non-solvation in D2O38. Nevertheless, this spectrum is very much useful for monitoring and determination of degree of quaternization of PDMAEMA segment of the graft copolymer. The spectrum clearly shows different methylene and methyl protons of propayl sultone units and DMAEMA units both in the quaternized and non-quaternized states. The signal at 2.9 ppm is a combination of methylene protons ‘r’ and residual N-methyl protons ‘zʹ’. However, after quaternization the signal corresponding to the methylene protons (– OCH2CH2–) shift to 3.85 ppm [designated as signal ‘y’ in Figure 1(c)].39 Therefore intensity ratio of signal ‘zʹ’ (derived after subtracting the signal intensity of ‘r’ protons from the signal at 2.85 ppm) and signal ‘y’ is used for calculation of the degree of quaternization. It shows

(b)

(a)

Figure 2. (a) Survey XPS scan of PVDMS (inset: enlarged portion of fluorine). (b) High resolution XPS spectra of N 1s core level of PVDMS.


Page 11 of 27 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Langmuir

about 66% of NMe2 groups present in PDMAEMA segments are quaternized. The high resolution XPS spectrum of N 1s core level of PVDMS (Figure 2b) also supports the degree of quaternisation. The XPS spectra can be close-fitting with two peaks corresponding to unquaternized amino group (-NMe2) of PDMAEMA segments at 400.2 eV and quaternized ammonium cation (-NMe3+) of PVDMS at 401.5 ev.40,41 The survey scan spectra (Figure 2a) confirms the presence of PVDF backbone due to the advent of F (1s) peak at 690 eV.42 The signals arising at 164.2 eV and 531.4 eV correspond to the S (2p) and O (1s) of the graft segments of PVDMS.41 In the FT-IR spectrum of PVDM-1 (Figure S2), shows the peaks at 532, 615, 761 cm-1 characterizing α-phase of pure PVDF.43 After grafting with PDMAEMA the intensity of α phase peak at 532 cm-1 has diminished shifting to 534 cm-1 and intensity of 761 cm-1 peak is also diminished showing a shift to 775 cm-1. But there appears new peaks at 840 and 1275 cm-1 corresponding to the formation of β-phase of PVDF indicating the formation of mixture of α and β phases.43 The strong peak at 1730 cm-1 depicts the presence of ester group of PVDM-1 supporting the successful grafting of PDMAEMA chains on PVDF backbone.5 In FTIR spectra of PVDMS the peaks at 605 cm-1 (–C-S- stretch), 1036 and 1178 cm-1(-S=O stretching of SO3-) are attributed to the characteristic peaks of sultone, justifying the formation of zwitterionic polymer on the modification of PVDM-1.44 Here it is important to note that characteristic peaks of α and β phases of PVDF are almost absent in the FTIR spectra. The WAXS pattern of PVDM, PVDM-1 and PVDMS are shown in the Figure 3 and the diffractograms of both PVDM and PVDM-1 exhibits major peaks at 2θ = 17.8 and 20.30 indicating presence of a mixture of α and β phases of PVDF crystal supporting the FTIR spectral results.45 β-polymorph PVDF chain is polar in nature with all trans conformation. 11 ACS Paragon Plus Environment

Langmuir

17.8

20.3

Intensity (a.u.)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 12 of 27

PVDM PVDM-1

PVDMS

5

10

15

20

25

2 (degree)

30

35

40

Figure 3. XRD spectra of PVDM, PVDM-1and PVDMS.

The supramolecular interaction between the dipolar >C=O group in the grafted chain and the >CF2 group of PVDF back bone46 helps to stabilize the nucleation of polar all trans conformation of PVDF. Hence β-polymorph PVDF is produced in the PVDM and PVDM-1 along with the nonpaolar α-polymorph having trans gauche trans gauche (TGTG) conformation. Here it is important to note that the intensity of crystalline peaks in PVDM-1 is much lower compared to that of the unfractionated PVDM sample. This is because of the presence of a larger amount of PDMAEMA in the PVDM-1 fraction compared to that of unfractionated PVDM sample decreasing the fraction of PVDF and the PVDF chain to form crystallites. This decrease of PVDF crystallization is dominated on zwitterion formation due to the hindrance of the diffusion of PVDF chains for strong ionic interaction of zwitterions showing the presence of amorphous peak in WAXS spectra supporting the FTIR spectra. The possible cause for the decrease of crystallinity in PVDMS is that PVDF chain is nonpolar and therefore it faces difficulty to enter through the ionic atmosphere of zwitterionic grafted chain via diffusion process for nucleation and growth of crystals.47


Page 13 of 27 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Langmuir

Morphology: The TEM images of PVDM-1 and PVDMS (Figure 4) present interesting morphology cast from the aqueous medium. In PVDM-1 there are small vesicular morphology (average dimension = 20 ± 2 nm). The vesicles may be formed due to self-organization of the hydrophobic PVDF chain at the centre and the pendent hydrophilic PDMAEMA chains are distributed both inward and outward directions. The PVDF chains may form small crystallites at the core forming stable spherical surface and inside and outside of it hydrophilic grafted PDMAEMA chains are well dispersed entrapping water inside the sphere producing the

(b)

(a)

Figure 4. TEM images of (a) PVDM-1 and (b) PVDMS. vesicles. During quaternization with sultone the external PDMAEMA chains of the vesicle are used, and the internal PDMAEMA chains have lesser chance for quaternization due to difficulty in diffusion of 1,3 propane sultone into the vesicle interior. The outer PDMAEMA chains after quaternization have positive charge on nitrogen atom and negative charge on the oxygen atoms of sultone. An inter-vesicle aggregation therefore occurs increasing the vesicle size from 20 to 100 ± 10 nm. The TEM image clearly indicates the self-organization of a large number of vesicles to form the compound vesicles. This self-organization is illustrated in a scheme 2. The hydrophobic and hydrophilic balance PVDM-1 guides the self-assembly


Langmuir 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Scheme 2. Schematic model for formation vesicle of PVDM-1 and its transformation to intervesicular aggregates in PVDMS via ionic interaction with enhancement of emission.

into vesicles causing the presence of PVDF chain within the vesicle walls and some part of PVDF chains are present outside. Zwitterion formation causes ionic interaction among the grafted chains shown in the scheme. These vesicles possess outer surface charges (shown with orange colour) resulting inter-vesicular aggregation. UV-Vis Spectra: The UV-Vis spectra of PVDM-1 and PVDMS in aqueous medium are presented in Figure 5a. From the figure it is evident that PVDM-1 has three adsorption peaks at 210, 276 and 457 nm with a hump at 430 nm. Though a definite origin of these absorption peaks are not known, the 210 peak may be arising from the ester group of the graft segments48, 49. The peak at 276 nm may be attributed to the intrachain n-π* transition from the amine to the carbonyl group of the 14 ACS Paragon Plus Environment

Page 14 of 27

Page 15 of 27 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Langmuir

(a)

(b)

Figure 5. (a) UV-vis absorption spectra and (b) Photoluminescence (PL) spectra of PVDM-1and PVDMS (0.25% w/v) in water. Excitation wavelength of PVDM-1 and PVDMS are 390 nm 370 nm respectively. pendent PDMAEMA chain present at the vesicle and the peak at 457 nm may arises due to the interchain n-π* transition19 occurring mainly at outer vesicle surface where possibility of interchain self-organization is very much likely. On the other hand in PVDMS

two

absorption peaks are noticed at 203 and 297 nm, the later peak is arising from the intrachain n-π* transition of the sultone group and the peaks at 430 and 457 nm disappear possibly due to the absence of interchain n-π* transition upon quaternization due to ionic repulsion. Fluorescence Spectra: The fluorescence spectra of PVDM-1 and PVDMS in aqueous medium are presented in Figure 5b. It is evident from the figure that PVDM-1 exhibits a broad fluorescence peak at 534 nm for excitation at 390 nm and the broadness may arise for different environment of nitrogen atoms of the grafted chains particularly situating inside and outside of the vesicle surface. PVDMS exhibit a sharp emission peak at 438 nm (for excitation at 370 nm) arising from the transition of excitons from sulfonate anion to quaternary ammonium ions which are mainly present at the outside of the vesicles. Also the increased intensity of PVDMS may be attributed to the aggregation induced emission where the quenching of the excitons by the solvent molecules is more restricted compared to that of PVDM-1 sample. The PVDM-1 solution shows fluorescence property with a low quantum yield (1%) in water whereas 15 ACS Paragon Plus Environment

Langmuir 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

PVDMS exhibits high fluorescence quantum yield of 8% supporting more aggregation induced emission due to zwitterion formation. This is very much comparable to the polymeric systems without any fluorophore reported earlier50-52. Zhu et al. reported 1.26% quantum yield from poly(vinyl alcohol) based non-conjugated polymer dots50 and recently Bhattacharya et al. reported 8.4% quantum yield using non-conjugated polymer nanodots51. It is to be noted here that the emission peak of PVDMS occurs at much lower wavelength than that of PVDM-1. A probable reason may be the stabilization of ground state due to delocalization of π-electrons for aggregation causing higher energy emission. 25,53 It is well known that PVDF is a non-fluorescent polymer. It shows a low emission property due to grafting with PDMAEMA and this property further improves by zwitterion formation of the grafted chains. This fluorescence property may be used to detect ionic surfactants in water. As an example, here fluorescence intensity enhances for aggregation both with the cationic (CTAB) and anionic (SDBS) surfactants (Figure S3a & S3b) due to decease of quenching of excitons with the solvent (water). However, this does not occur in neutral surfactant (Triton X-100) (Figure S4), so it can differentiate the ionic and neutral surfactant in aqueous medium. Theoretical Discussion: To have an insight into the optimized polymeric structures of PVDM-1 and PVDMS and also to construct their MOs, DFT calculations are made. Three repeating units of these polymers are used as model for simplification of theoretical calculations. It is found that in PVDM-1, HOMO is localized mainly on the terminal tertiary amine moiety on the tail and LUMO is focused on the carbonyl group (Figure 6a). On the other hand, for PVDMS, the scenario for LUMO is totally different; LUMO is localized primarily on the quaternary amine group, this is in accord with the electron deficiency on the quaternary amine group. HOMO of PVDMS is located on the electron rich terminal sulphonate unit (Figure 6b). Absorption maxima for 16 ACS Paragon Plus Environment

Page 16 of 27

Page 17 of 27 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Langmuir

Figure 6. Computed HOMO and LUMO plots for (a) PVDM-1 and (b) PVDMS. Hydrogen atoms are omitted for clarity. Black, blue, dark red and dark yellow colors are used to assign carbon, oxygen, nitrogen and sulphur atoms respectively. both the model structures were also calculated by time-dependent density functional theory (TDDFT). The data are summarized in Table S1. More equivalency of the data may be reached by considering higher number of repeating units, but this is beyond our reach due to our limitation in computing. The Molecular orbitals associated with the electronic transitions for PVDM-1 and PVDMS are represented in Figure S5 and S6 respectively. Energy diagram of selected molecular orbitals are shown in Figure S7. The electronic transitions of PVDM-1 at 276, 430 and 457 nm are attributed due to the transitions from HOMO to LUMO+2, HOMO to LUMO+1 and HOMO-2 to LUMO, respectively. In the case of PVDMS, the peak at 297 nm is assigned for the transition from HOMO-8 to LUMO+1. Here it is worth mentioning that in the optimized model of PVDM-1, the average distances between electron rich tertiary amine unit and their neighboring electron deficient carbonyl units are 4.82, 4.72 and 3.75 Å (See Figure 7a). Whereas in case of model of zwitterionic PVDMS, the average distances between electron deficient ternary amine unit and 17 ACS Paragon Plus Environment

Langmuir 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Figure 7. Optimized ground state structure for (a) model PVDM-1, (calculated bond distances (in Å) between nitrogen of tertiary amine and carboxyl unit are given) and (b) model PVDMS (calculated bond distances (in Å) between nitrogen of quaternary ammonium unit and Sulphur and oxygen atoms of sulphonate unit are given). neighboring donor sulphonate group are 4.04, 4.15 and 3.69 Å (See Figure 7b). This result indicates that modification of repeating unit in case of PVDMS, decreases the distance between donor and acceptor units. Such coiling effect makes the model more compact and hence prevents non radiative decay process.19 This phenomenon explains more intense emission in PVDMS than PVDM-1. Conclusion: So we are able to make PVDF, a non-conjugated polymer, to be fluorescence active by quaternization of PVDF-g-PDMAEMA from a highly soluble fraction PVDM-1 with propyl sultone. The morphology of PVDM-1 changes from small vesicle to large aggregated vesicle of quaternized PVDMS. The PDMAEMA units of the outer surface of PVDM-1 vesicles are only quaternized during post polymerization modification. After quaternization the absorption peak at visible region disappear and the n-π* absorption peak shows a small red shift than that of PVDM-1. The broad emission peak of PVDM-1 becomes sharper upon quaternization showing a 10 fold increase of emission intensity emitting at higher energy. The emission intensity further increases on aggregation with ionic surfactants but remains 18 ACS Paragon Plus Environment

Page 18 of 27

Page 19 of 27 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Langmuir

unchanged on addition of neutral surfactant. From, theoretical calculations using trimeric model system of PVDM-1 and PVDMS, origin of their emission can be ascribed as n-π interactions. For PVDM-1, the interaction involves lone pair of tertiary amine group and empty π of carbonyl group and in case of PVDMS, interaction between lone pairs on terminal sulphonate group and empty π of quaternary ammonium group occurs. Acknowledgments: We acknowledge Prof. Sreebrata Goswami, School of Chemical Sciences, IACS, for helping in theoretical calculations. We also acknowledge SERB (grant number EMR/2016/005302) for financial support. M. P acknowledges UGC, New Delhi; R.G. and S.P.R gratefully acknowledge CSIR, New Delhi for providing fellowship. Supporting Information: APC traces of PVDM, PVDM-1; FTIR spectra of PVDM, PVDM-1, PVDMS; fluorescence spectra on addition of surfactants and details of theoretical calculations are presented in supporting information. The Supporting Information is available free of charge on website. References: 1. Heste, J. F.; Banerjee, P.; Won, Y.Y.; Akthakul, A.; Acar, M. H.; and Mayes, A. M. ATRP of Amphiphilic Graft Copolymers Based on PVDF and Their Use as Membrane Additives. Macromolecules. 2002, 35, 7652-7661. 2. Andrew, J. S; Clarke, D. R. Effect of Electrospinning on the Ferroelectric Phase Content of Polyvinylidene Difluoride Fibers. Langmuir. 2008, 24, 670-672. 3. Kuila, A.; Chatterjee, D. P.; Maity, N.; Nandi, A. K. Multi-Functional Poly(Vinylidene Fluoride) Graft Copolymers. J. Polym. Sci., Part A: Polym. Chem. 2017, 55, 2569-2584. 19 ACS Paragon Plus Environment

Langmuir 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

4. Jana, K. K.; Prakash, O.; Shahi, V. K.; Avasthi, D. K.; Maiti, P. Poly(vinylidene fluoride-co-chlorotrifluoro ethylene) Nanohybrid Membrane for Fuel Cell. ACS Omega 2018, 3, 917−928. 5. Samanta, S., Chatterjee, D. P.; Manna, S.; Mandal, A.; Garai, A.; Nandi, A. K. Multifunctional Hydrophilic Poly(vinylidene fluoride) Graft Copolymer with Supertoughness and Supergluing Properties. Macromolecules. 2009, 42, 3112-3120. 6. Martins. P.; Lopes, A. C.; Lanceros-Mendeza, S. Electroactive phases of poly(vinylidene fluoride): Determination, processing and applications. Prog. Polym. Sci. 2014, 39, 683-706. 7. Das, S.; Routh, P.; Ghosh, R.; Chatterjee, D. P.; Nandi, A. K. Water-Soluble Ionic Polythiophenes for Biological and Analytical Applications. Polym. Int. 2017, 66, 623639. 8. Luo, X.; Lu, Z.; Xi, J., Wu, Z.; Zhu, W.; Chen, L.; Qiu, X. Influences of Permeation of Vanadium Ions through PVDF-g-PSSA Membranes on Performances of Vanadium Redox Flow Batteries. J. Phys. Chem. B. 2005, 109, 20310-20314. 9. Liang, S.; Kang, Y.; Tiraferri, A.; Giannelis, E. P.; Huang, X.; Elimelech, M. Highly Highly Hydrophilic Polyvinylidene Fluoride (PVDF) UltrafiltrationMembranes via Postfabrication Grafting of Surface-Tailored Silica Nanoparticles. ACS Appl. Mater. Interfaces. 2013, 5, 6694-6703. 10. Lowe, A. B.; and McCormick, C. L. Synthesis and Solution Properties of Zwitterionic Polymers. Chem. Rev. 2002, 102, 4177-4189. 11. Chen, S.; Li, L.; Zhao, C.; Zheng, J. Surface hydration: Principles and applications toward low-fouling/nonfouling biomaterials. Polymer. 2010, 51, 5283-5293.


Page 20 of 27

Page 21 of 27 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Langmuir

12. Yang, Q.; Ulbricht, M.; Novel Membrane Adsorbers with Grafted Zwitterionic Polymers Synthesized by Surface-Initiated ATRP and Their Salt-Modulated Permeability and Protein Binding Properties. Chem. Mater. 2012, 24, 2943−2951. 13. Laschewsky, A.; Rosenhahn, A.; Molecular Design of Zwitterionic Polymer Interfaces:

Searching

for

the

Difference

.Langmuir.

DOI:

10.1021/acs.langmuir.8b01789. 14. Das, S.; Chatterjee, D. P.; Ghosh, R.; Nandi, A. K. Water soluble polythiophenes: preparation and applications. RSC Adv. 2015, 5, 20160-20177. 15. Lin, Y.; Gao, J-W.; Liu, H-W.; Li, Y-S. Synthesis and Characterization of Hyperbranched Poly(ether amide)s with Thermoresponsive Property and Unexpected Strong Blue Photoluminescence. Macromolecules. 2009, 42, 3237-3246. 16. Lee, W. I.; Bae, Y.; and Bard, A. J. Strong Blue Photoluminescence and ECL from OH-Terminated PAMAM Dendrimers in the Absence of Gold Nanoparticles. J. Am. Chem. Soc. 2004, 126, 8358-8359. 17. Wu, D.; Liu, Y.; He, C.; Goh, S. H. Blue Photoluminescence from Hyperbranched Poly(amino ester)s. Macromolecules. 2005, 38, 9906-9909. 18. Wang, D.; Imae, T.; Fluorescence Emission from Dendrimers and Its pH Dependence. J. Am. Chem. Soc. 2004, 126, 13204-13205. 19. Li. W.; Che, C.; Pang, J.; Cao, Z.; Jiao, Y.; Xu, J.; Ren, Y.; Li, X.; Autofluorescent Polymers: 1H,1H,2H,2H‑Perfluoro-1-decanol Grafted Poly(styrene‑b‑acrylic acid) Block Copolymers without Conventional Fluorophore. Langmuir. 2018, 34, 53345341. 20. Wang, Y.; Jiang, G.; Sun, X.; Ding, M.; Hub, H.; Chen, W.; Preparation of shell cross-linked nanoparticles via miniemulsion RAFT polymerization. Polym. Chem. 2010, 1, 1638-1643. 21 ACS Paragon Plus Environment

Langmuir 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

21. Zhu, S.; Song, Y.; Shao, J.; Zhao, X.; Yang, B.; Non-Conjugated Polymer Dots with Crosslink-Enhanced Emission in the Absence of Fluorophore Units. Angew. Chem. Int. Ed. 2015, 54, 14626-14637. 22. Yan, J. J.; Wang, Z. K.; Lin, X. S.; Hong, C. Y.; Liang. H. J.; Pan, C. Y.; You, Y. Z. Polymerizing Nonfluorescent Monomers without Incorporating any Fluorescent Agent Produces Strong Fluorescent Polymers. Adv. Mater. 2012, 24, 5617–5624. 23. Feng, T.; Zhu, S.; Zeng, Q.; Lu, S.; Tao, S.; Liu, J.;Yang, B. Supramolecular CrossLink-Regulated Emission and Related Applications in Polymer Carbon Dots. ACS Appl. Mater. Interfaces. 2018, 10, 12262−12277. 24. Chu, C. C.; Imae, T. Fluorescence Investigations of Oxygen-Doped Simple Amine Compared with Fluorescent PAMAM Dendrimer. Macromol. Rapid Commun. 2009, 30, 89−93. 25. Pucci, A.; Rausa, R.; Ciardelli, F. Aggregation-Induced Luminescence of Polyisobutene Succinic Anhydrides and Imides. Macromol. Chem. Phys. 2008, 209, 900−906. 26. Wang, R. B.; Yuan, W. Z.; Zhu, X. Y. Aggregation-induced emission of nonconjugated poly(amido amine)s: Discovering,luminescent mechanism understanding and bioapplication. J. Polym. Sci. 2015, 33, 680-687. 27. Kundu, A.; Layek, R. K.; Kuila, A., and Nandi, A. K. Highly Fluorescent Graphene Oxide -Poly(vinyl alcohol) Hybrid: An Effective Material for Specific Au3+ Ion Sensors. ACS Appl. Mater. Interfaces. 2012, 4, 5576-5582. 28. Frisch, M. J. T., G. W.; Schlegel, H. B.; Scuseria, G. E.; Robb, M. A.; Cheeseman, J. R.; Scalmani, G.; Barone, V.; Mennucci,B.; Petersson, G. A.; Nakatsuji, H.; Caricato, M.; Li, X.; Hratchian, H.P.; Izmaylov, A. F.; Bloino, J.; Zheng, G.; Sonnenberg, J. L.; Hada, M.; Ehara, M.; Toyota, K.; Fukuda, R.; Hasegawa, J.; Ishida, M.; Nakajima,T.; 22 ACS Paragon Plus Environment

Page 22 of 27

Page 23 of 27 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Langmuir

Honda, Y.; Kitao, O.; Nakai, H.; Vreven, T.; Montgomery, J. A., Jr.; Peralta, J. E.; Ogliaro, F.; Bearpark, M. J.; Heyd, J.; Brothers, E. N.; Kudin, K. N.; Staroverov, V. N.; Kobayashi, R.; Normand, J.; Raghavachari, K.; Rendell, A. P.; Burant, J. C.; Iyengar, S. S.; Tomasi, J.; Cossi, M.; Rega, N.; Millam, N. J.; Klene, M.; Knox, J. E.; Cross, J. B.; Bakken, V.; Adamo, C.; Jaramillo, J.; Gomperts, R.; Stratmann, R. E.; Yazyev, O.; Austin, A. J.; Cammi, R.; Pomelli, C.; Ochterski, J. W.; Martin, R. L.; Morokuma, K.; Zakrzewski, V. G.; Voth, G. A.; Salvador, P.; Dannenberg, J. J.; Dapprich, S.; Daniels, A.D.; Farkas, Ő.; Foresman, J. B.; Ortiz, J. V.; Cioslowski, J.; Fox, D. J.: Gaussian 09. Gaussian, Inc: Wallingford, CT 2009. 29. Hariharan, P. C.; Pople, J. A.: Influence of polarization functions on MO hydrogenation energies. Theor. Chim. Acta 1973, 28, 213-22. 30. Stratmann, R. E.; Scuseria, G. E.; Frisch, M. J.: An efficient implementation of timedependent density-functional theory for the calculation of excitation energies of large molecules. J. Chem. Phys. 1998, 109, 8218-8224. 31. Bauernschmitt, R.; Ahlrichs, R.: Treatment of electronic excitations within the adiabatic approximation of time dependent density functional theory. Chem. Phys. Lett. 1996, 256, 454-464. 32. Casida, M. E.; Jamorski, C.; Casida, K. C.; Salahub, D. R.: Molecular excitation energies to high-lying bound states from time-dependent density-functional response theory: characterization and correction of the time-dependent local density approximation ionization threshold. J. Chem. Phys. 1998, 108, 4439-4449. 33. Cossi, M.; Rega, N.; Scalmani, G.; Barone, V.: Energies, structures, and electronic properties of molecules in solution with the C-PCM solvation model. J. Comput. Chem. 2003, 24, 669-681.


Langmuir 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

34. Cossi, M.; Barone, V.: Time-dependent density functional theory for molecules in liquid solutions. J. Chem. Phys. 2001, 115, 4708-4717. 35. Barone, V.; Cossi, M.: Quantum Calculation of Molecular Energies and Energy Gradients in Solution by a Conductor Solvent Model. J. Phys. Chem. A 1998, 102, 1995-2001. 36. O'Boyle, N. M.; Tenderholt, A. L.; Langner, K. M.: Software news and updates cclib: a library for package-independent computational chemistry algorithms. J. Comput. Chem. 2008, 29, 839-845. 37. Hester, J. F., Banerjee, P., Won, Y.-Y., Akthakul, A., Acar, M. H., and Mayes, A. M. ATRP of Amphiphilic Graft Copolymers Based on PVDF and Their Use as Membrane Additives. Macromolecules. 2002, 35, 7652-7661. 38. S.B. Lee, A.J. Russell, K. Matyjaszewski. ATRP synthesis of amphiphilic random, gradient, and block copolymers of 2-(dimethylamino)ethyl methacrylate and nbutyl methacrylate in aqueous media. Biomacromolecules. 2003, 4, 1386–1393. 39. Zhu, Y.; Noy, J-M.; Lowe, A. B.; Roth, P. J. The synthesis and aqueous solution properties of sulfobutylbetaine (co)polymers: comparison of synthetic routes and tuneable upper critical solution temperatures. Polym. Chem., 2015, 6, 5705–5718. 40. Yang, X.; Zhang, B.; Liu, Z.; Deng, B.; Yu, M.; Li, L.; Jianga, H.; Li, J.; Preparation of the antifouling microfiltration membranes from poly(N,Ndimethylacrylamide) grafted poly(vinylidene fluoride) (PVDF) powder. J. Mater. Chem., 2011, 21, 11908– 11915. 41. Ghosh, R.; Das, S.; Bhattacharyya, K.; Chatterjee, D. P.; Biswas, A.; Nandi, A. K. Light-Induced Conformational Change of Uracil-Anchored Polythiophene-Regulating Thermo-Responsiveness. Langmuir. 2018, 34, 12401−12411.


Page 24 of 27

Page 25 of 27 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Langmuir

42. Kuila, A.; Chatterjee, D. P.; Layek, R. K.; Nandi, A. K. Coupled atom transfer radical coupling and atom transfer radical polymerization approach for controlled grafting from poly(vinylidene fluoride) backbone. J. Polym. Sci., Part A: Polym. Chem. 2014, 52, 995–1008. 43. Maity, N.; Mandal, A.; Nandi, A. K. High dielectric poly(vinylidene fluoride) nanocomposite films with MoS2 using polyaniline interlinker via interfacial interaction. J. Mater. Chem. C, 2017, 5, 12121—12133. 44. Zhai, S.; Ma, Y.; Chen, Y.; Li, D.; Cao, J.; Liu, Y.; Cai, M.; Xie, X.; Chena, Y. ; Luo X. Synthesis of an amphiphilic block copolymer containing zwitterionic sulfobetaine as a novel pH-sensitive drug carrier. Polym. Chem., 2014, 5, 1285–1297. 45. Gaur, A.; Kumar, C.; Tiwari, S.; Maiti, P. Efficient Energy Harvesting Using Processed Poly(vinylidene fluoride) Nanogenerator. ACS Appl. Energy Mater. 2018, 7, 3019-3024. 46. Samanta, S., Chatterjee, D. P., Layek, R. K., Nandi, A. K. Multifunctional Porous Poly(vinylidenefluoride)-graft-Poly(butyl

methacrylate)

with

Good

Li+

Ion

Conductivity. Macromol. Chem. Phys. 2011, 212, 134–149. 47. Hoffman, J. D., Davis, G. T., Lauritzen, J.I., Jr. In ‘Treatise on Solid state Chemistry, N.B. Hannay Ed. Plenum Press, New York. 1976; Vol-3, pp 497. 48. Ikbal, M., Banerjee, R., Barman, S., Atta, S., Dhara, D., Singh, N. D. P. 1Acetylferroceneoxime-based photoacid generators: application towards sol–gel transformation and development of photoresponsive polymer for controlled wettability and patterned surfaces. J. Mater. Chem. C. 2014, 2, 4622-4630. 49. Tsurumi, S., Wada, S. Identification of 3-(0--Glucosyl)-2-Indolone-3-Acetylaspartic Acid as a New Indole-3-Acetic Acid Metabolite in Vicia Seedlings. Plant Physiol.1985, 79, 667-671. 25 ACS Paragon Plus Environment

Langmuir 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

50. Zhu, S., Zhang, J., Wang, L., Song, Y., Zhang, G., Wang, H., Yang, Bai. A general route to make non-conjugated linear polymers luminescent. Chem. Commun., 2012, 48, 10889–10891. 51. Bhattacharya, A., Mukherjee, T. K. Synergistic Enhancement of Electron-Accepting and –Donating Ability of Nonconjugated Polymer Nanodot in Micellar Environment. Langmuir. 2017, 33, 14718−14727. 52. Zhu, S.; Song, Y.; Shao, J.; Zhao, X.; Yang, B. Non-conjugated Polymer Dots with Crosslink-enhanced Emission in the Absence of Fluorophore Units. Angew. Chem., Int. Ed. 2015, 54, 14626−14637. 53. Mei, J.; Leung, N. L. C.; Kwok, R. T. K. ; Lam, J. W. Y.; Tang, B. Z.; AggregationInduced Emission: Together We Shine, United We Soar! Chem. Rev. 2015, 115, 11718−11940.


Page 26 of 27

Page 27 of 27 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Langmuir

TOC Zwitterionic Poly(vinylidene fluoride) Graft Copolymer with Unexpected Fluorescence Property Mahuya Pakhiraa, Radhakanta Ghosha, Santi P. Rathb Dhruba P. Chatterjeec and Arun K. Nandi*


Zwitterionic Poly(vinylidene fluoride) Graft Copolymer with

Recommend Documents