Temperature Responsive Gels Based on Pluronic F127 and Poly(vinyl alcohol)

Abstract

Aqueous mixtures of Pluronic F127 and poly(vinyl alcohol) (20% polymer concentration in the system) were prepared and investigated by rheology and laser particle size distribution, in order to obtain temperature responsive gels for biomedical applications. The influence of the gelation conditions and system composition on the viscoelastic parameters and particle size distribution (which are very sensitive to the sol-gel transition process) was followed. The investigations realized at physiological temperature (37°C) showed the thixotropic profile of the gels, the yield stress induced by the Pluronic presence, and the high elasticity evidenced in the creep-recovery tests.

pH influence on rheological and structural properties of chitosan/poly(vinyl alcohol)/layered double hydroxide composites

“…7 shows the curves which represent the viscoelastic response for the hybrid hydrogel at three applied stresses in creep tests (1 Pa, 30 Pa and 50 Pa, respectively) followed by recovery. In these pH conditions (weakly acid or basic), the behaviour of physical CS/PVA/LDH hydrogels in creeprecovery tests is similar to those observed for other physical hydrogels [33]. The degree of recovered strain (c rec ) is above 70% of the maximum value reached by the strain in the creep test for shear stress up to 120 Pa (Fig.…”

In situgelation of aqueous solutions of entangled poly(vinyl alcohol)

“…For the present study: t F (1) ¼ 100 min, t F (2, 3, ., n) ¼ 50 min and t A (1, 2, ., n) ¼ 50 min, n being the number of freezing/thawing/ageing cycles. Since the rheological parameters (G 0 , G 00 , tan d, shear or complex viscosity) are very sensitive to the sol-gel transition process, 34,35 they were systematically recorded during heating above 0 C and then during ageing, interesting PVA structural changes were expected to occur. Once the gel structure was formed, the polymer system reaches an equilibrium reected by constant values of the dynamic moduli and viscosity.…”

Rheological investigation of poly(vinyl alcohol)/poly(N-vinyl pyrrolidone) mixtures in aqueous solution and hydrogel state

“…If the aqueous solutions of PVA are subjected to several freezing/thawing cycles, hydrogels are formed with a porous, strong, rubbery elastic structure [1][2][3]. By mixing PVA with other natural [4,5] or synthetic [6] polymers, new composites can be obtained which synergetically combines the properties of individual components. In order to prepare materials for biomedical applications, an interesting partner for PVA is PVP [7][8][9][10].…”

“…The hydrogels can be obtained using different chemical or physical methods [1][2][3][4][5][6][7][8][9][10][14][15][16][17][18][19][20][21][22][23][24][25]. Chemical crosslinking provides a more controllable network structure with uniform pore sizes but requires a careful purification step to remove the free unreacted crosslinker, initiator or monomers with potential toxicity.…”

“…Chemical crosslinking provides a more controllable network structure with uniform pore sizes but requires a careful purification step to remove the free unreacted crosslinker, initiator or monomers with potential toxicity. Physical methods allow the hydrogel formation by physical interactions between macromolecules occuring in well established conditions and, in some cases, their properties and performances are comparable or even superior to those of the chemical hydrogels, as for example reversible sol-gel transition to external stimuli, such as temperature [6] or pH [4,20]. Cryogelation method was applied to PVA containing systems in order to obtain physical hydrogels with high elasticity [1-3, 5, 18, 22-24, 26], excellent swelling and long term stability [26] and very good weight-bearing properties [23], characteristics highly explored in pharmaceutical [1], biomedical and bioengineering applications [1-3, 5, 18, 22, 23, 26].…”