Phase Transition Behavior of Hydroxypropylcellulose under Interpolymer Complexation with Poly(acrylic acid)

Abstract

The phase transition behavior of hydroxypropylcellulose (HPC) under interpolymer complexation with poly(acrylic acid) (PAA) has been studied by turbidity and laser light scattering measurements. It has been found that the lower critical solution temperature (LCST) of the HPC was drastically reduced after adding 1 wt % of PAA into the HPC solution. The LCST of the HPC/PAA complexes decreased with the increase of the molecular weight of either the HPC or the PAA. The driving force shifting the LCST is attributed to the hydrogen bonding and hydrophobic interaction of the macromolecules. As the pH value increases from at 4.0 to 6.0, the LCST of the HPC−PAA complex decreases. This may be due to the salt effect of the polyelectrolyte on the nonionic polymer. The HPC/PAA complexation has been observed even at very dilute solution of 1.6 × 10-5 g/mL at pH = 3.2. The study of complexation between the HPC and the PAA leads to a new method for synthesis of surfactant-free microgels at room temperature. The resultant microgels swell and collapse at the pH value higher and lower than the pK α value of the PAA, respectively.

Gels from acrylic acid and hydroxypropyl cellulose via free radical polymerization

“…PAA gives a yellowish colour and HPC gives a bluish one. Divinyl sulfone (DVS) was used as a crosslinker for HPC [7,8,11]. Initially, the experiment used glutaraldehide [12] as a crosslinker, however it was changed to DVS because many gels dissolved in water, thus yielding a poor degree of crosslinking and low percentages of absorbed water.…”

“…The HPC phase transition may be caused by the delicate hydrophilic-hydrophobic balance of the HPC itself, which has a large bipolar moment. When the temperature is increased, the bipolar moment is reduced, and the HPC phase transition occurs [7]. HPC has been used as a raw material for artificial muscles; high concentrations have the biggest moduli but less elasticity, and thus, are easier to break [8].…”

“…HPC has been used as a raw material for artificial muscles; high concentrations have the biggest moduli but less elasticity, and thus, are easier to break [8]. Lu et al [7] studied the phase transition behaviour of HPC under interpolymer complexation with PAA, creating several mixtures of HPC and PAA, starting with the polymer, and not the monomer, of PAA. It was found that with pure HPC, nanospheres are formed at 41 °C, and microspheres at room temperature.…”

Synthesis and Self-Assembly Behavior of Temperature Responsive 2-Hydroxy-3-Isopropoxypropyl Hydroxyethyl Cellulose

“…尽管此类生物基温度敏感高分子的生物相容性 和生物降解性显著提高, 然而调节其 LCST 相对困难, 并且可调控范围小, 这为在不同领域中的实际应用带来 了困难. 羟丙基纤维素(HPC)被认为是具有温敏性能的 水溶性纤维素衍生物, 当温度高于其 LCST 时, HPC 从 水溶液中沉淀出来, 但是 HPC 的 LCST 较高(45～ 65 ℃), 并且不方便调节 [14,15] . 为了克服以上不足, 本 课题组以多糖及其衍生物为主链通过简单的醚化反应 将不同类型的疏水基团接枝到主链上, 通过调节多糖骨 架的亲油亲水平衡值, 制备了一系列不同类型的刺激响 应型多糖基智能材料 [16,17] .…”

Polymeric Hydrogel Nanocapsules: A Thermo and pH Dual-responsive Carrier for Sustained Drug Release

“…Then the polymerization of NIPAm was carried out at 35 o C under a nitrogen stream and magnetic stirring. The reaction kept on for another 2 h before being cooled down to the room temperature, resulting in the HPC-PAA-PNIPAm complex particles.…”