Polymer Bulletin

, Volume 69, Issue 7, pp 827–846 | Cite as

New pH-responsive linear and crosslinked functional copolymers of N-acryloyl-N′-phenyl piperazine with acrylic acid and hydroxyethyl methacrylate: synthesis, reactivity, and effect of steric hindrance on swelling

Original Paper


New functional linear copolymers and crosslinked gels based on a disubstituted heterocyclic acrylamide, i.e., N-acryloyl-N′-phenyl piperazine (AcrNPhP) with acrylic acid (AA) and hydroxyethyl methacrylate (HEMA) were prepared by thermal free-radical polymerization. The composition of the linear copolymers was analyzed by infra-red spectral analysis and elemental analysis methods. The reactivity parameters of the monomers were determined by the Finemann-Ross and Kelen–Tüdös linearization methods. Using the values obtained from the Kelen–Tüdös linearization methods, the reactivity or resonance stabilization (Q) and polarity (e) of AcrNPhP with AA and HEMA were calculated (AcrNPhP–AA system Q = 1.9, e = −0.6, and AcrNPhP–HEMA system Q = 2.5, e = −1.2). Crosslinked copolymer hydrogels of AcrNPhP with AA and HEMA were prepared by bulk and solution polymerization methods. The method of preparation, the type of crosslinker and monomers showed a profound impact on the pH responsive swelling of the gels. The hydrogels were highly responsive to changes in external pH. The gels composed of AcrNPhP and AA swelled more than 1,200 % above the pKa of acrylic acid. Interestingly, no significant swelling (about 1 %) was observed in solution of low pH (acidic) despite the presence of an ionizable tertiary amine function in the polymer network. This is attributed to the presence of a bulky phenyl group at the tertiary amine function of AcrNPhP which sterically hinders the protonation and thereby the final swelling of the gel. The gels composed of AcrNPhP and HEMA did not display a significant pH responsive behavior due to the same effect. The AcrNPhP–HEMA gel-containing 70 % AcrNPhP swelled to only 50 % despite the presence of a large fraction of the ionizable unit.


N-acryloyl-N′-phenyl piperazine Acrylic acid Hydroxyethyl methacrylate Reactivity ratios pH-responsive Reactivity ratio 


  1. 1.
    Gonzalez N, Elvira C, San Román J (2005) Novel-dual stimuli responsive polymers derived from ethyl pyrrolidine. Macromolecules 38:9298–9303CrossRefGoogle Scholar
  2. 2.
    Chen G, Hoffman AS (1995) Graft copolymers that exhibit temperature-induced phase transitions over a wide range of pH. Nature 373:49–51CrossRefGoogle Scholar
  3. 3.
    Galaev YI (1995) Smart polymers in biotechnology and medicine. Russ Chem Rev 64:471–490CrossRefGoogle Scholar
  4. 4.
    DeRosa ME, DeRosa RL, Noni LM, Hendrick ES (2007) Phase separation of poly(N-isopropylacrylamide) solutions and gels using near IR fiber laser. J App Polym Sci 105:2083–2090CrossRefGoogle Scholar
  5. 5.
    Sershen SR, Westcott SL, Halas NJ, West JL (2002) Independent optically addressable nanoparticles polymer optomechanical composites. App Phys Lett 80:4609–4611CrossRefGoogle Scholar
  6. 6.
    Peppas NA, Bures P, Leobandung W, Ichikawa H (2000) Hydrogels in pharmaceutical formulation. Eur J Pharm and Biopharm 50:27–46CrossRefGoogle Scholar
  7. 7.
    Katime I, Mendizabal E (2010) Swelling properties of new hydrogels based on the dimethyl amino ethyl acrylate methyl chloride quaternary salt with acrylic acid and 2-methylene butane-1,4-dioic acid monomers in aqueous solutions. Mat Sci Appl 1:162–167Google Scholar
  8. 8.
    Cakal E, Cavus S (2010) Novel poly(N-vinylacprolactam-co-2-(diethylamino)ethyl methacrylate) gels: characterization and detailed investigation on their stimulisensistive behaviors and network structure. Ind Eng Chem Res 49:11741–11751CrossRefGoogle Scholar
  9. 9.
    Brazel CS, Peppas NA (1995) Synthesis and characterization of thermo and chemomechanically responsive poly(N-isopropylacrylamide-co-methacrylic acid) hydrogels. Macromolecules 28:8016–8020CrossRefGoogle Scholar
  10. 10.
    Siegel RA (1993) Responsive gels: volume transitions 1. In: Dusek K (ed) Advances in Polymer Science. Springer, BerlinGoogle Scholar
  11. 11.
    Hoffman AS (1997) In: Park K (ed) Controlled drug delivery: challenges and strategies. American Chemical Society, WashingtonGoogle Scholar
  12. 12.
    Nash MA, Lai JJ, Hoffman AS, Yager P, Stayton PS (2010) Smart diblock copolymers as templates for magnetic core gold shell nanoparticles synthesis. Nano Lett 10:85–91CrossRefGoogle Scholar
  13. 13.
    Kim B, Peppas NA (2002) Synthesis and characterization of pH-sensitive glycopolymers for oral drug delivery systems. J Biomater Sci Polym Edn 13:1271–1281CrossRefGoogle Scholar
  14. 14.
    Krishna Rao KSV, Ha CS (2009) pH sensitive hydrogels based on acrylamides and their swelling and diffusion characteristics with drug delivery behaviour. Polym Bull 62:167–181CrossRefGoogle Scholar
  15. 15.
    Peppas NA, Huang Y, Lugo MT, Ward JH, Zhang J (2000) Physicochemical foundations and structural design of hydrogels in medicine and biology. Annu Rev Biomed Eng 2:9–15CrossRefGoogle Scholar
  16. 16.
    Saitoh T, Suzuki Y, Hirade M (2002) Preparation of poly(N-isopropylacrylamide)-modified glass surface for flow control in microfluidics. Anal Sci 18:203–208CrossRefGoogle Scholar
  17. 17.
    Dong LC, Hoffman AS (1986) Thermally reversibly hydrogels: III. Immobilization of enzymes for feedback reaction control. J Cont Rel 4:223–227CrossRefGoogle Scholar
  18. 18.
    Plunkett KN, Moore JS (2004) Patterned dual pH-responsive core–shell hydrogels with controllable swelling kinetics and volumes. Langmuir 20:6535–6537CrossRefGoogle Scholar
  19. 19.
    Gao Y, Au-Yeung SCF, Wu C (1999) Interaction between surfactant and poly(N-vinylcaprolactam) microgels. Macromolecules 32:3674–3677CrossRefGoogle Scholar
  20. 20.
    Gan LH, Gan YY, Roshan Deen G (2000) Poly(N-acryloyl N′-propyl piperazine) a new stimuli responsive polymer. Macromolecules 33:7893–7897CrossRefGoogle Scholar
  21. 21.
    Roshan Deen G, Gan YY, Gan LH, Teng SH (2011) New functional copolymers of N-acryloyl-N′-methyl piperazine and 2-hydroxyethyl methacrylate: synthesis, determination of reactivity ratios and swelling characteristics of gels. Polym Bull 66:301–313CrossRefGoogle Scholar
  22. 22.
    Roshan Deen G, Gan LH (2006) Determination of reactivity ratios and swelling characteristics of stimuli responsive copolymers of N-acryloyl-N′-ethyl piperazine and MMA. Polymer 47:5025–5034CrossRefGoogle Scholar
  23. 23.
    Roshan Deen G, Gan LH (2008) Influence of amino group pKa on the properties of stimuli responsive piperazine-based polymers and hydrogels. J Appl Polym Sci 107:1449–1458CrossRefGoogle Scholar
  24. 24.
    Gan LH, Goh NK, Chen B, Chu CK, Roshan Deen G, Chew CH (1997) Copolymers of N-acryloyl-N′-methyl piperazine and methyl methacrylate: synthesis and its application for Hg(II) detection by anodic stripping voltammetry. Eur Polym J 33:615–620CrossRefGoogle Scholar
  25. 25.
    Danusso F, Tanzi MC, Levi M, Martini A (1977) Polymers and copolymers of N-acryloyl-N′-phenyl piperazine. Polymer 31:1577–1580CrossRefGoogle Scholar
  26. 26.
    Fineman M, Ross SD (1950) Linear methods for determining monomer reactivity ratios in copolymerization. J Poly Sci 5:259–262CrossRefGoogle Scholar
  27. 27.
    Kelen T, Tüdös F (1975) Analysis of the linear methods for determining copolymerization reactivity ratios. A new improved linear graphic method. J Macromol Sci Chem A9:1–27Google Scholar
  28. 28.
    Malawska B, Goaille S (1995) Search for new anticonvulsant compounds. Pharmazie 50:722–725Google Scholar
  29. 29.
    Nair CPR, Clouet G, Brossas J (1988) Functionalization of vinyl polymers through polymeric iniferters. Polymer 29:1909–1917CrossRefGoogle Scholar
  30. 30.
    Alfrey T Jr, Price C (1947) Relative reactivities in vinyl copolymerizations. J Poly Sci 2:101–106CrossRefGoogle Scholar
  31. 31.
    Brandrup J, Immergut EH (1989) Polymer handbook. Wiley, New YorkGoogle Scholar
  32. 32.
    Igarashi S (1963) Representation of composition and blockiness of the copolymer by a triangular coordinate system. Polym Lett 1:359–363CrossRefGoogle Scholar
  33. 33.
    Bartil T, Bounekhel M, Cedric C, Jerome R (2007) Swelling behavior and release properties of pH-sensitive hydrogels based on methacrylic derivatives. Acta Pharm 57:301–314CrossRefGoogle Scholar
  34. 34.
    Byun H, Hong B, Nam SY, Jung SY, Rhim JW, Lee SB, Moon GY (2008) Swelling behaviour and drug release of poly(vinyl alcohol) hydrogel crosslinked with poly(acrylic acid). Macromol Res 16:189–192CrossRefGoogle Scholar
  35. 35.
    Gan LH, Roshan Deen G, Loh XJ, Gan YY (2001) New stimuli-responsive copolymers of N-acryloyl-N′-alkyl piperazine and methyl methacrylate and their hydrogels. Polymer 42:65–69CrossRefGoogle Scholar
  36. 36.
    Gan LH, Roshan Deen G, Gan YY, Tam KC (2001) Water sorption studies of new pH responsive N-acryloyl-N′-methyl piperazine hydrogels. Eur Poly J 37(1473):1477Google Scholar
  37. 37.
    Mathur AM, Moorjani SK, Scranton AB (1996) Methods for synthesis of hydrogel networks. Rev Macromol Chem Phys C36:405–430CrossRefGoogle Scholar
  38. 38.
    Flory PJ (1969) Principles of polymer chemistry. Cornell Univeristy Press, LondonGoogle Scholar
  39. 39.
    Bajpai SK, Singh S (2006) Analysis of swelling behavior of poly(methacrylamide-co-methacrylic acid) hydrogels and effect of synthesis conditions on water uptake. React Funct Polym 66:431–440CrossRefGoogle Scholar
  40. 40.
    Peppas NA, Barr-Howell BD (1986) In: Peppas NA (ed) Hydrogels in medicine and pharmacy, vol 1: fundamentals. CRC Press, Boca RatonGoogle Scholar
  41. 41.
    Caykara T, Küçüktepe S, Turan E (2007) Swelling characteristics of thermo sensitive poly[(2-diethylaminoethyl methacrylate)-co-(N,N-dimethylacrylamide)] porous hydrogels. Polym Int 56:532–537CrossRefGoogle Scholar

Copyright information

© Springer-Verlag 2012

Authors and Affiliations

  1. 1.Soft Materials Laboratory, Natural Sciences and Science Education, National Institute of EducationNanyang Technological UniversitySingaporeSingapore

Personalised recommendations